What are the risks of many bounces between the surface and 15-20' / 5-7m of water?

[boulderjohn]

my bad, signing off now... going to my reading lesson

I misread it the first time, too.

What the OP is getting in this instance is called a sawtooth profile, and it is not highly recommended. There has not been a lot of research done on it, though. When I dived the cenotes in Mexico, I was given a similar warning. They are shallow, and it is very easy to do a lot of up and down during the dive. Again, I don't have any hard evidence to which I can point, but my inclination would be to avoid it.

 

[dumpsterDiver]

Good point dumpster. My 2 reasons are that as a shell collector you can cover much more ground (even in 5 feet depth) with scuba rather than going up & down. Also, with a 7 mil wetsuit scuba makes sense.

5 feet deep and scuba diving? Cover more ground? Unless the visibility is really bad, I can cover more ground easier and quicker and for longer without wearing a tank....But hey, this is for fun.. who am I to say anything about how you have fun...

Maybe I should add something of value. Mixing freediving and scuba is generally frowned upon. On the other hand, when I was a lot younger, I used to swim a raft offshore and then scuba dive in 20 feet for 80 minutes maybe (mostly getting lobster) and then put the tank in the raft and freedive at the same depth for another few hours shooting fish (doing maybe 50 additional dives) and then tow the raft in. I never had anything bad happen, but I don't think I would be that aggressive, now that I know better.

 

[spectrum]

I don't see any good coming from this. My first thoughts were in line with the experience TS&M related. Profound fatigue after a dive day with a few too many ascents and we weren't all that deep either. The potential for ear issues was a good point too.

If this gets combined with any near term typical scuba diving I can't imagine how it may play out.

If you go ahead with this how about a rich nitrox?

Pete

 

[MXGratefulDiver]

some would say.. for depths of 10-30 feet, why even bother with scuba gear?

Oh some might say that, but they'd be missing out. This time of year some of my favorite dives are 20 feet or less. The eelgrass beds are a nursery, and spending time there is pure theater. I bother with scuba gear because (a) the best time to be there is when it's dark ... that's when all the action happens, and (b) on a single LP95 I can stay there for a couple hours.

I can give you hundreds of reasons to bother ... I'll try to limit it to a few, though ... all of this was going on in between 7 and 20 feet ...

My only sighting ... ever ... of a Hudspeth Sapsucker nudibranch ... maybe three-quarters of an inch long, feeding on the plankton that collected on a piece of eelgrass ...

Schools of tubesnouts provide food for many species of creatures who come to the eelgrass beds for dinner ...

Snailfish seem to prefer the shallower depths, inhabiting the spaces between eelgrass beds ...

Several species of marine creatures lay their eggs in the eelgrass beds. Hatchlings, like this tiny plainfin midshipman, can only be seen there. This one's less than an inch long ...

... and this juvenile longfin sculpin isn't much larger ...

... and all those tiny fish attract larger fish ... like gunnels ...

... and my favorite little fish ... Pacific Spiny Lumpsuckers ... commonly found in the eelgrass beds between October and March ... this one's about two-thirds the size of a ping-pong ball ...

Despite the vivid colors on some of these creatures, the reality is that they blend in pretty well with their surroundings ... they have to if they want to live to become adults. Even at very shallow depths, the chances of finding them while freediving are much less than on scuba ... and without scuba the chances of staying down there long enough to get a good picture are not very good. For that reason, shallow eelgrass dives are becoming more and more popular here in winter.

Many divers get too focused on how deep they can go. Marine creatures, on the other hand, often prefer habitats that only grow in shallower waters. Those divers who visit these shallow habitats often discover a diversity of life that deeper waters just don't offer ...

... Bob (Grateful Diver)

 

[dumpsterDiver]

Oh some might say that, but they'd be missing out. This time of year some of my favorite dives are 20 feet or less. The eelgrass beds are a nursery, and spending time there is pure theater. I bother with scuba gear because (a) the best time to be there is when it's dark ... that's when all the action happens, and (b) on a single LP95 I can stay there for a couple hours.

I can give you hundreds of reasons to bother ... I'll try to limit it to a few, though ... all of this was going on in between 7 and 20 feet ...

My only sighting ... ever ... of a Hudspeth Sapsucker nudibranch ... maybe three-quarters of an inch long, sitting on a piece of eelgrass ...

Schools of tubesnouts provide food for many species of creatures who come to the eelgrass beds for dinner ...

Snailfish seem to prefer the shallower depths, inhabiting the spaces between eelgrass beds ...

Several species of marine creatures lay their eggs in the eelgrass beds. Hatchlings, like this tiny plainfin midshipman, can only be seen there. This one's less than an inch long ...

... and this juvenile longfin sculpin isn't much larger ...

... and all those tiny fish attract larger fish ... like gunnels ...

... and my favorite little fish ... Pacific Spiny Lumpsuckers ... commonly found in the eelgrass beds between October and March ... this one's about two-thirds the size of a ping-pong ball ...

Despite the vivid colors on some of these creatures, the reality is that they blend in pretty well with their surroundings ... they have to if they want to live to become adults. Even at very shallow depths, the chances of finding them while freediving are much less than on scuba ... and without scuba the chances of staying down there long enough to get a good picture are not very good. For that reason, shallow eelgrass dives are becoming more and more popular here in winter.

Many divers get too focused on how deep they can go. Marine creatures, on the other hand, often prefer habitats that only grow in shallower waters. Those divers who visit these shallow habitats often discover a diversity of life that deeper waters just don't offer ...

... Bob (Grateful Diver)

Very nice photos... and I personally do understand why people would scuba in shallow water, but I was just being my usual PIA. My freedive buddies would kinda laugh at scuba in 5-8 feet, but again this is for FUN.. Some people build doll houses for fun...I used to enjoy taking macro photos in relatively shallow water.

It is funny that several people have mentioned ear trouble... why would this be any more of an issue than for a typical freediver?

 

[MXGratefulDiver]

Very nice photos... and I personally do understand why people would scuba in shallow water, but I was just being my usual PIA. My freedive buddies would kinda laugh at scuba in 5-8 feet, but again this is for FUN.. Some people build doll houses for fun...I used to enjoy taking macro photos in relatively shallow water.

It is funny that several people have mentioned ear trouble... why would this be any more of an issue than for a typical freediver?

I don't know ... seems the mechanics would be the same, since it's ambient pressure, rather than breathing pressurized gas, that's the culprit ... and that would be the same regardless.

I do know, however, that people who do a lot of ups and downs in shallow water ... such as instructors conducting ESA exercises ... sometimes experience ear problems due to all the pressure changes ...

... Bob (Grateful Diver)

 

[dumpsterDiver]

I don't know ... seems the mechanics would be the same, since it's ambient pressure, rather than breathing pressurized gas, that's the culprit ... and that would be the same regardless.

I do know, however, that people who do a lot of ups and downs in shallow water ... such as instructors conducting ESA exercises ... sometimes experience ear problems due to all the pressure changes ...

... Bob (Grateful Diver)

That's probably because those instructors can't really freedive?

 

[@dam]

Thanks for all the input. I came across this study that said breaking a dive into several segments with time spent on the surface is actually safer than one long dive (assuming, of course, that proper ascent procedures are used)

http://www.hse.gov.uk/research/rrpdf/rr214.pdf

This is because you get to get rid of some nitrogen mid-dive.