Ok. As a scuba diver this was... a bit painful to watch.
Where do we begin?
Total disregard for safety. They penetrate a wreck, which is dangerous enough to do when you got scuba gear, but when you are snorkeling and got only one breath in your lungs? Come on!
They all run out of air at one point or another, which brings results in a few funny things. Sure, you can get excited and forget to check your airsupply, but I thought these were experienced divers? And what's with no octopus (backup 2nd stage to share air with a buddy in an emergecny)? Any trained diver will have one, it's essential standard equipment. Then we have the rapid ascents, sure they are not That deep, but that's just dangerous. This movie disregards most of the basic safety rules of scuba diving just to get more action.
Again with the huge underwater explosions that seemingly have no effect what so ever on divers real close.
Also, no one seems to care at all about preserving the archeological finds. I thought these were suppose to be the good guys vs the evil ones?
I can let the way way long breaths slide since people can train themselves to hold their breath for several minutes.
Ok, let's review the actual movie without the technical issues.
Predictable plot. Shallow characters.
Not much else to say really. Only waste time on this if you are really obsessed with Jessica Alba.