This has been bothering me for a few weeks.

We went to Ocean City, MD last month and spent a day crabbing with
chicken legs and string. We caught enough crabs in a few hours to feed
the 6 of us.

I mistakenly assumed that since the crabs live in the water I should
transport them back to our condo in water, so I put enough water in
the cooler to cover them. They were all pretty feisty during the few
hours we were catching them and tossing them in the cooler.

However, a couple of hours later when we got back to the condo, 90% of
them were dead.

I later learned that they should be transported on ice with a roughly
50 degree temp being the best.

The thing I don't get is why did they die in the cooler in just a
couple of hours? In all the time we were crabbing I never saw one crab
"come up for air" so I assume that they can breath in water.

Did they simply use up all of the oxygen in the cooler water and
basically drown?