Tag Archives: Freediving

Sporasub SP1 Freediving Computer / Watch Review

The latest addition to my growing list of freediving kit is my new Sporasub SP1 freedive computer. This helps me with one or two of my frustrations which I am sure that I share with other new freedivers. How deep am I going? How long am I down for? How many dives have I done? One of the reasons I prefer freediving over scuba is the simplicity, so I really don’t want to clutter my body or my thought processes with anything more than i have to.

This is the perfect tool for me; as well as satisfying my curiosity, I con now benchmark one day’s diving against the next to see how my performance is changing over time.

Why did I go for the Sporasub SP1? Well, I started at the bottom of the price range (this cost £145 or $225), and worked upwards, luckily my criteria were satisfied by this one, which happens to be the cheapest on the market. It was also dropping in prices as the new Sporasub SP2 is available with wireless connection and heart rate monitor, and I wanted to snap one of these up before they stop making it.

Sporasub SP1 Time display mode

Sporasub SP1 Time display mode

What I wanted was simple:-

  1. Something that automatically kicked in to log dives without me having to remember to press any buttons.
  2. Something that allowed me to look at logs afterwards to see what I had done
  3. Something that logged surface time as well as dive time

What I didn’t want:-

  1. A scuba watch that also had a freedive function (watches with more than one button are confusing enough for me without having loads of extra functions I will never use).
  2. Something that relied on me having to press buttons before every dive (something else confusing that I can’t be bothered with).
  3. To spend double just to get extra functions that I won’t ever use unless I start training and competing at deep diving.
Sporasub SP1 Dive log Mode

Sporasub SP1 Dive log Mode, showing depth, water temp, and dive duration

What you get with the Sporasub SP1 freedive computer:-

  1. Dive mode automatically kicks in when the watch is submerged by 1.5m, you don’t have to do anything, it just starts logging straight away, even if the last time you looked it was just showing the time.
  2. When you get back to the surface it automatically starts to count surface time (you should be breathing up on the surface for at least as long as your last dive before you go down again)
  3. It logs dive time, dive depth accurate to 10 cm, water temperature.
  4. It saves these records for you to look at later, up to 199 of them.
  5. Depth warning, it will beep for 30 seconds when you reach a preset limit.
  6. Switch between sea and fresh water
  7. Other stuff you would normally get on a watch, time, date, stopwatch etc.

Things you might get on a more expensive computer that the Sporasub SP1 doesn’t have:-

  1. Wireless link to a heart rate monitor (like the Sporasub SP2)
  2. USB connection to download and analyse your dive stats and save them for ever more. (Sporasub SP2, Mares Smart Apnea, Oceanic Aeris F10)
  3. Time warning, multiple depth warnings, (Oceanic Aeris F10)
  4. hydration reminders, descent and ascent speeds (Mares Smart Apnea)

Summary – It works first time and every time, logging all the dives I do accurately (when compared to another borrowed dive computer strapped to my leash in a recent test dive).

I found the controls a little infuriating to start with when I tried to look at the dive starts whilst the screen was still displaying surface time. But this is more about my not remembering the instructions than design fault.

Who would I recommend this for? Any recreational non competitive freediver or spearo who wants an easy way to log their dives.

Who would I not recommend this for? More serious competition divers who want to really monitor things like ascent speeds, who need 10m warnings and want to monitor heart rates while diving. Those guys probably want to go for something more swanky, but they are going to pay in the region of £100 to £200 more for these functions.

Am I happy with the SP1? Yes. It looks cool too, though my wrists are so skinny I won’t be wearing it as a fashion accessory.

Boyle’s Law for the Shallow Freediver

One of the basic things we learn at school, and probably don’t think about again until we start to dive is Boyle’s Law – Simply put – As pressure doubles, volume halves (given constant temperature and some other stuff).

This is also something that is taught as part of any freediving course (or scuba), as it helps us understand the physiology, and the dangers, of gas expansion or compression in the context of diving.

So any freediver will have seen the table that illustrates that at 10m down the pressure has increased from 1 atmosphere to two and the volume in our lungs has halved. And when we get to 20m despite this being double the depth the pressure is only 3 atmospheres so it isn’t until you get to 30m where pressure will be 4 atmospheres, (double what it was at 10m) that the volume will be halved again, 1/4 of what it was at the surface.

Whilst this is a great help in illustrating the principle, the reality is the when we start diving we aren’t thinking in terms of 20 or 30m, the difficulties we need to overcome are all in the first 10m, and srangely there isn’t really a table anywhere on the internet that illustrates what happens in this band, until now!

I used an online Boyle’s Law calculator to work out what happens to our lung volume in the first 15m, and illustrate it, with a comparison to the deeper changes, for me and all to see forever more. Let’s hope it is correct.

So…..

Boyles Law for Freedivers

Boyles Law for Freedivers

The reduction for each stage shown in the right hand column illustrate how the rate of change drops rapidly with depth.

From this table we can make a few observations….

  • If you duck dive and put your lungs where your fins were (say 2.5m), the air in your lungs has already reduced by 20% and you have experienced the quickest build up of pressure than at any other time  in your dive.
  • We all know that by diving to 10m our lung capacity is halved, but of that half, very little is lost between 7.5m and 10m, most of it is before that, (7% between 7.5 and 10m, compared with 20% between the surface and 2.5m.
  • You only have to get down to the 12.5 – 15m zone and the differences are relatively small.
  • The volume of air lost between the surface and 2.5m is roughly the same as that which is lost between 20m and 70m.

I have found that with the practice I have had, equalising comes much more easily over these first couple of metres than it used to. Without thinking I do a frenzel manouvre as I turn to dive which seems to free things up in the first metre, then grab my nose after I have started to straighten out and drop, this means after my fins have submerged and I have made the first kick, which puts me down at 3m, there isn’t a build up of pressure.

A boat dive, and an interesting refresher

So yesterday I joined a boat dive. FreediveUK were taking out a couple of AIDA 2* students and they sometimes take previous students out to get a bit more practice. There were two main reasons why I joined the boat trip; firstly to get some depth experience. It is difficult to find deeper water shore diving where I live so since my course none of the dives I have done have been more than about 10m. Secondly I was sold on the great visibility they are getting down in Cornwall at the moment. I haven’t experienced more than about 5m since I qualified and I was looking forward to being wowed out by the clarity.

Unfortunately only one of these was achieved, I got some extra depth but the weather was atrocious and the viz was some of the worst I have seen (do you see poor viz, or not see it?), in fact it couldn’t have been worse, at the surface you could barely see your hand at arm’s length, beyond about 12m was darkness!

This trip was also an opportunity to get used to my new freediving watch, the Sporasub SP1, but more of that later.

The second site that the knowledgeable dive boat skipper (Mark from Atlantic Scuba) found was just calm enough, and deep enough to drop the rope to 16m. As soon as we got into the water and I saw how poor the viz was I had quite a deja vu for my own 2* course, over a year ago in that cold dark quarry. The first few free immersions down to about 10m were fine, but when it came to clipping on the leash and diving down the rope I got all tangled again and faced the embarrassment of not being able to achieve what the other two guys were about to do.

It is funny how a few extra things to think about make it so much more difficult. Where previously I have been building confidence with every dive, suddenly I felt like I was back to square one, a few seconds aligning myself with an almost invisible rope, trying to pinch my nose with the hand to which the leash was attached, and suddenly I hadn’t equalised properly. It all started feeling a bit alien and before you know it I had turned at 8m, a depth that last week I was doing without even thinking about it.

Luckily while they were going through their drills with the instructor I had a practice doing some variable weight dives with the dive-master. This is simply holding on to a heavy weight whilst he controls the descent of rope over the first critical couple of meters, then he lets it drop. The prospect of descending at rate over which you have almost no control is slightly daunting the first time, but as soon as you feel any discomfort you can just let go, the weight speeds to the bottom and you pull yourself up on the rope as usual. The advantage of this practice is that it removes all factors from the equation apart from equalisation. You don’t have to move, fin or worry about anything else. It came surprisingly easy and was a real confidence booster, especially at depth, when it suddenly became so dark you couldn’t see any contrast in the light at all, and the only way of knowing where was up was the direction of the rope.

My watch told me that I was mostly dropping the weight around 12 or 13m, I think this was due to slightly painful sinuses, and proved I needed to maybe descend more slowly. I’m not sure if this kind of descent is suitable for very new beginners, if you don’t know how well you equalise, or aren’t aware of the warning signs then you should probably be careful.

As soon as I got back on the other rope I finned straight down to 16.4m (couldn’t see the plate at all!) and came slowly back up all nice and comfy, no problems, relaxed descent, and much more relaxed in the darkness.

The things I learn’t from this trip were:-

1/ I have to admit I’m really not comfortable yet at depth in very low viz. My lungs give me all the time in the world, and in clear water I am happy to stop and hang around for 10 or 15 seconds to equalise, get my bearings, align to a rope, (or just look at fishes), then carry on. But as it gets darker I will turn at the slightest hint of a problem, I’ll overcome that and yesterday was a confidence booster.

2/ The first dive or two of the day beyond about 8m result in an immediate urge to breathe, my body subconsciously thinking I need to breathe because my lung capacity has quickly halved (nearly) these contractions, (just like when you do breath hold practice) interfere with equalisation and cause confusion. That feeling goes away after the first couple of dives and this helps with keeping calm and no longer interferes with equalisation.

Louis Shield Wreck

A second test of my GoPro Hero2 underwater housing – Another lesson Learned

Well today we visited my most local beach as I knew the visibility was going to be good and I hoped to see some of the big barrel jellyfish that are swarming up the coast at the moment. Unfortunately I didn’t see any, but the viz was probably about 6-8m and there was plenty of other stuff to see.

Unfortunately I have learned the hard way about the standard GoPro Hero2 underwater housing. It doesn’t focus properly underwater! What! I think it is fair to assume that an underwater housing good for 40m will actually take reasonable pictures underwater, but no, I got it wrong. I need the flat lens dive housing. The standard one, although waterproof to 40m doesn’t actually work properly underwater, it is still really just meant for surfing etc. where it is expected to take pictures above water.

You can see a short video here that illustrates the problem (apologies for the spelling mistake).

It is colourful, and the subject matter would be quite interesting, but it never going to be great until the focus problem is sorted so watch this space for some more impressive video when I get a new housing.

The trip was still worthwhile, the local wreck, Louis Shield is just off the rocks. There are some bits in open sand in the middle of the bay, on a very low spring tide these are just visible. Today the top was about 2m down, and 4m to the sand and tangled with old nets and lobster pots, quite dangerous in fact. The bulk of the wreck is just off the rocks, again this is almost too shallow to dive sometimes.

Louis Shield Wreck

Loius Shield Wreck

 

My new GoPro Underwater Housing – More to learn!

Yesterday I took my new GoPro housing and underwater selfie stick for a test. I have had a GoPro camera for a long time so I am used to the benefits and otherwise of using it, but this is the first time I have tried it underwater. The housing was watertight, that’s the main thing, so I haven’t lost a camera. Other than that, well, let’s just say I don’t have much to publish that will win me any awards. Part of this is due to the fact that the water was so cloudy, full of bloom and microscopic stuff which left everything looking green. That and the fact that there wasn’t much marine life around to photograph, a few small crabs on the sandy bottom to follow, one big ugly spider crab, and no fish. I didn’t even look great when I turned it on myself. Nothing to look at here!

Deep – James Nestor – A great book about Freediving and other ocean stuff

DeepJamesNestor

I am partial to a freediving book, as I am partial to endless YouTube videos of people going up and down in endless blue and doing weird underwater stunts, to an extent which my wife doesn’t understand, so when the book ‘the Deep’ by journalist James Nestor came out I was at the front of the queue.

Firstly he deals with freediving as an outsider, a journo sent to cover a competition in Greece. There he sees what in a way is the seedier side of freediving, people pushing themselves to their limits. Blackouts and evacuations to hospital have the potential to give a bad reputation to what is statistically quite a safe sport, but through the people he meets there he is soon drawn into a wondrous world where competition is only a small part of why people feel driven to dive into a place where, for a minute or two at a time, they can forget they are human and be part of something different.

He goes on to learn from the experts, which includes not only how to dive, but how freedivers interact with the ocean environment and what some of them are achieving in research and conservation. Some of this isn’t necessarily conducted in a strict academic environment, he visits projects that are conducted and/or financed by informed but unqualified individuals rather than academic institutions. This is why he makes reference in the subtitle to ‘renegade science’ but in a way this makes it all the more interesting as individuals pursue interests that might be a little too off piste or dangerous for academics to risk their reputations, or even their lives; think diving unprotected with sharks or sperm whales. Whatever your views on this I am envious of the year he spent chasing down material for this book, and the things he learn’t along the way.

Well worth a read.

Apnea Camo Spearfishing Suit

Time for a New Wetsuit

The wife doesn’t approve of this at all, it is neither fashionable, flattering nor practical, but it might get me a fish.

I went to Spearfishingstore.co.uk otherwise known as Venture Sports, they are a specialist shop in Paignton, Devon, which happens to be not far away from where I live. They are a dive shop who specialises in spearfishing / freediving stuff.

They are really really helpful, can’t do enough for you and full of good advice. I had already bought a few essentials from them, knife, weights, fins etc. But this time I couldn’t resist the great price they offered me on a speargun, so the suit cost me a lot more than I bargained for, but hey, I’m a fully camouflaged spearfisherman and well equipped marine forager now, it will pay for itself in food within the week I am sure!

My suit is an Apnea one. I tried on the examples they have in the shop as they won’t let you ruin a brand new one. Unfortunately the one bought seems a lot tighter, very tight, in fact so tight I took it back and made them let me try a brand new XL, but that was too big, so I hope that the one I have will stretch. Today, having nearly dislocated my shoulder getting it on I spent a while waddling round the garden in it, I think it will stretch.