I don't know the answer to your question, but I'm sure that folks on this forum will know:

http://www.scubaboard.com/forums.php

If you go to the "diving physiology" sub-forum and post your question you'll get plenty of good advice from docs.

Kona Honu divers at www.konahonudivers.com is a great outfit. Do the night manta dive...it's amazing (and even lower energy since on the second dive you just sit around and do nothing but watch the mantas dance with each other. I don't know about doing a dive before the IM, but I always do that dive 3-4 days before the HIM.

I've been a certified diver for almost 30 yrs, assistant instructor, working dive master and had a part time summer scuba charter business.

It's not the physical effort but the nitrogen/blood build up on occuring on extended bottom time that may effect a diver. If you become saturated you can actually in rare cases develop "the bends" after doing a serious exercise load afterwards even if you were OK after the dive.

However, this is highly unlikely since becoming blood/nitrogen saturated means pushing the limits beyond recommended bottom times. We used to do wreck diving in the Great Lakes, pushed bottom times to the max, multiple daily dives, and I never had the bends in over 1000 such dives. This was also diving on air in very cold water at depths past 120 ft which is very hard on the body physiology. If you follow the rules, diving is a safe sport. Ignore them and you're taking huge risks.

You folks are dive newbies and are doing Hawaii shore diving in warm water/high visability and I'd assume probably in relatively shallow depths. This is low stress diving. Do the dive and take the rest of the day off. It won't effect your performance in the tri.

BTW, my wife is doing the World's in Oz in November then we're going to the Great Barrier Reef to dive.

Take a class for Enriched Air (Nitrox) certification. You can stay down longer, plus you'll be getting more oxygen into your blood. Hmmm, good pre-race activity?

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Proud member of FISHTWITCH: doing a bit more than fish exercise now.

Thanks for the advice. I think I'll give it a go.

Grant

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Grant