Cool! Boyle's Law, not Archimedes' principle ... LOL
I'm assuming most of the carbonation is gone at those depths?
I think the carbonation is still there but the pressure keeps it in solution, it isn't outwardly fizzy
Ah, you're right!
Found this on Google :
When you're situated beneath the ocean, the pressure outside is so high that it forces the bubbles back into the liquid, hence no explosion. Also, beverages opened at depth will stay carbonated longer too.