If water could be pressurised, how low would the sea level be due to the pressurising weight of the overlying water?

A small spherical projectile made of glass, about 1/4 inch in diameter, would be too influenced by wind to much to go, consistantly, the farthest.  On the opposite hand, a larger spherical projectile made of glass, say 6 inches in diameter, would not be affected by the wind, but may be too heavy and have too much mass to travel to far..  Say the pressure was 10 psi for all sizes of projectiles, what size would the projectile be for optimum distance?

I hope that the changes in the description and the question clarify some things.

I've been dropping squash balls at different temperatures from a constant height of 1m, and measuring the height they bounce up to. I understand that as you heat the squash balls, air molecules inside the ball (which has negligible increases in mass and volume) bounce again each other and the inside of the ball more often and harder, leading to more air pressure in the ball, and thus a higher bounce. Is there any equation that links pressure or temperature with a drop height and bounce height? I've been using Boyle's law, Charles law and the pressure law to find pressure, and there are existing formulae for volumes, of course, but how can I link pressure with bounce? I assume it will involve the coefficient of restitution somewhere, but I'm unsure. Thanks a lot! :)

I've always wondered if, with enough pressure, it were possible to compress water into a solid shape, and have it remain that way.