@Just_Gabe:
Even if they were 2000 mts it would be impossible to survive, how do you swim back to the surface 2 whole kms in less than 30 secs? But well, this is OP and Oda could pull something ridiculous like pell's survival.
I believe there is speculation that when a bubble bursts it coats the nearest humans or something to that effect. Besides how deep was Zoro when he cut the ship?
If you're going to get caught up on the logistics you're taking a manga [about people getting superhuman powers via fruit - an oxygenated moon - floating islands of landmass covered in enormous trees suspended by clouds - ships being able to sink to depths of 10,000 leagues/feet/metres (whatever is being used) by being coated in only an oxygen filled bubble that should by laws of physics float not submerge.] A little too seriously.
It works because it needs to work - suspension of disbelief is not just a luxury it's a requirement, if there is a way to make it work great if not then it works because he needs it to work. A lot of writers take advice from all sources of information - but if something is declared impossible to do in real life then sometimes the writers just go ahead and do it the way they wanted to.
Matthew Reilly is a prime example of this thinking.