Multilevel diving and rock bottom.

[pengwe]

The metric version is 30 litres/minute (per diver), which is a little higher. I guess 28.3 is not so easy to work with.

Another question, what is your absolute Rock Bottom, i.e. the lowest you would ever go? (I see Rjack said 2-300psi) I ended up in an argument with my buddy about this. In 10' of water, on top of a reef covered in tropical fish life, warm water, great viz, no current, calm on the surface, the boat a few yards away.

 

[TSandM]

Well, I blew a tank down to about 300 psi this summer, chasing a jellyfish in about six feet of water. (That was an amazing day, with more than 40 feet of viz in Puget Sound, and we were in the water over 80 minutes on a single tank.) I blew an HP100 even lower than that (there was still gas under pressure in it!) the first dive I ever did with Mo2 and HBIwantmymoney'sworthoutofa130Girl. In ten feet of water, I was watching my pressure gauge in a kind of horror. You have to understand that I NEVER see pressures that low -- I get anxious when I get below 1000 psi!

 

[CompuDude]

The metric version is 30 litres/minute (per diver), which is a little higher. I guess 28.3 is not so easy to work with.

Another question, what is your absolute Rock Bottom, i.e. the lowest you would ever go? (I see Rjack said 2-300psi) I ended up in an argument with my buddy about this. In 10' of water, on top of a reef covered in tropical fish life, warm water, great viz, no current, calm on the surface, the boat a few yards away.

Totally depends on circumstances. Working with a class, I rarely get below 1000 psi, even though working dives tend to be short and shallow... not uncommon for two dives on one tank, to get that low.

In scary seas off a boat in the middle of the ocean, I'm going to want more cushion. In good conditions, an easy shore dive, with equally experienced buddies, I don't have an issue sucking my tanks down to 200 psi or so, although once I'm below 400 psi I'll want to be in 15' of water or less. Essentially, once I'm positive I can practically stand up and breathe if I need to, I don't worry too much about the "500 psi 'rule'"... but only in the right circumstances.

 

[b1gcountry]

I've breathed tanks down before, but I knew I was doing it. One time was in a pool doing DM skills, and I just wanted to get as far as possible before we had to stop. Another time I was swimming back to the platform at Mermet, and I just decided to swim back at 5' instead of on the surface because it was hot. I wound up with around 200psi. In normal situations, I try not to go below 500, but if finishing my safety stop means going below 500, I'm going to do it (and then figure out what I did wrong afterwards).

Tom