Really long, shallow no-deco dives

[magicwanz]

I don't recall anyone that I am familiar with doing a shallow recreational 4 hour open circuit dive.....anyone on this thread done one and why?

BUGS!!! 10-15ft BUGS!!!

 

[magicwanz]

If only going 10-20 feet, then maybe just skin dive?

BUGS!!! Blowing Bubbles a much better option in poor vis to cover more area when you can't see bottom at 10ft, hard to get good coverage in poor vis from the surface....

 

[BHB ScubaTroll]

I don't recall anyone that I am familiar with doing a shallow recreational 4 hour open circuit dive.....anyone on this thread done one and why?

Yes, me...

Venice Beach... Single HP 149. 4 1/2 hours. The only reason I surfaced... I got hungry. I still had 1,500 PSI left in the tank. Shark tooth hunting, and I love being underwater. It's very quiet and peaceful... On this particular day, my flag was being messed with and I could hear a boat above me idle up, idle down, idle up and idle down... I surface (to give the boat a mouth full of words)... It was a marine patrol boat... They asked me to move to another area so Sea Tow could tow a sail boat that was abandoned. They were worried that I was in the line Sea Tow would need to pull the boat off the shore. I moved, and when I surfaced the next time, all that stuff was gone.

Recreational 4.5 hour dive for relaxation and recreation

 

[HowardE]

I haven't quite done a 4 hour dive, but I've done 2.5 hour dives with a 72 cu ft tank, and have more than a 1/3 of my gas left (diving to 15 FSW in front of my apartment in Ft Lauderdale)

I usually get cold after 2 hours in a wet suit.

If I went down with a 120 or greater, I could easily do 4 hours on one of these dives.

There is plenty of reef structure, to keep someone occupied on a dive that long in Lauderdale by the sea (or vicinity)

 

[Charlie99]

I don't recall anyone that I am familiar with doing a shallow recreational 4 hour open circuit dive.....anyone on this thread done one and why?

I don't do 4 hour dives, but have done several 2+ hour dives on shore dives in Maui around 20-25' average depth. Usually just hanging out watching the fishies. With a beanie and 5mm wetsuit in 78F water, I'm nice and comfy and would probably spend more time if I had a tank bigger than AL80.

Time passes very quickly if you settle in and are doing things like watching the parade of fish coming to a cleaning station, or decide to follow an eel + grouper hunting party.

I also would easily have done a 4 hour bottom time when making a detailed map of a reef.

 

[DeepSeaExplorer]

Aren't ALL dives "deco" dives?

NOPE!

 

[DeepSeaExplorer]

I don't recall anyone that I am familiar with doing a shallow recreational 4 hour open circuit dive.....anyone on this thread done one and why?

I do also...

I dive from shore and want to maximize the time. Since it's a 45-60 minute swim each way, it doesn't make sense for a single tank dive. In August, when the water gets warm, sometimes I take a stage, that's when I start hitting the 4 hour mark. That's 4 hours of bottom time.

And no, I don't do a safety stop because it's not a deco dive, usually.

 

[JohnE]

Rookie question - I wonder if dive tables developers took much long, shallow dive data into account? Also I would imagine that in shallows it would be difficult not to end up going sawtooth between 30 and very shallow sometimes. This would be a bad thing, right?

It does seem like commercial divers doing boat repair would have a lot of experience with this. They may also have the problem of sawtooth like the previous poster mentioned with the bulkhead inspection.

 

[DeepSeaExplorer]

Rookie question - Also I would imagine that in shallows it would be difficult not to end up going sawtooth between 30 and very shallow sometimes. This would be a bad thing, right?

The only issue is that it could be hard on the ears, but there's no decompression issue. Even after 4 hours at 30 to 45 feet, I can go straight to the surface with no safety stop, and then swim hard for an hour with no decompression concerns.

If I go to the third reef (70fsw) and get into deco, I swim back underwater to the second reef. The deco obligation is gone before I get back to the second reef where I swim around for as long as I have gas remaining. Obviously, once the dive becomes a deco dive, the rules about bouncing and stops change.

 

[Charlie99]

Rookie question - I wonder if dive tables developers took much long, shallow dive data into account?
...
It does seem like commercial divers doing boat repair would have a lot of experience with this. ...

The USN tables are well suited for tracking very long, shallow dives, even repetitive ones.

The developers of the US Navy tables definitely took this sort of diving into account since a good portion of the their diving at that time was surface supplied divers working on ships. To properly account for such long, shallow dives, the USN tables use the 120 minute compartment as the controlling compartment (i.e it is the one on which the repetitive groups are based).

OTOH, the PADI table is based upon the 60 minute compartment. The controlling compartment in typical open circuit dives is 60 minutes or faster. By using the 60 minute compartment instead of the 120 min compartment to track pressure groups/repetitive dive calculations, the PADI tables better track normal open circuit scuba loadings and allow significantly longer repetitive dives than do the USN and USN derived (NAUI, SSI, YMCA, ...) tables. The PADI tables account for long, shallow dives through the ad hoc W,X, Y, Z rules that require either 1hour or 3 hour minimum surface intervals for 3 or more repetitive dives that get up into the highest loading levels.

Charlie Allen