A few comments:
1) When deep diving and the gases start affecting your head, I believe that is called nitrogen narcosis. Which sounds like about the same as getting drunk and losing your ability to reason and make decisions.
2) The body cannot withstand infinite or even very much pressure. For example, after about one or two hundred feet, people can skin dive. With have to start using pressure suits or submarines to go deeper.
3) On a heavier grav world, the water pressure will be even greater, because water pressure depends upon the density of the water (which probably won't change too much, because as stated above, water is mostly incompressible), how many feet down you are and what gravity is. So if you're on a planet with 2 times Earth's grav, water pressure will be twice as much as normal for each foot down.
4) Actually the earth isn't accelerating as it rotates, its moving at a constant angular velocity, so I don't that the rotational speed will have too much effect on gravity.
5) Besides gravity is determined by mass of the planet times a constant term dividing by the distance from the center squared. So a really small really dense body can have a much greater gravity the Earth, think neutron star or black hole. While a really large object that is not dense could have a lighter gravity. So the gravity on the exosolar planets would depend on their densities as well as their diameters.
Sorry for the long rant, I just tried to address some of the questions above.