If you're standing in water and want to get rid of it quickly, you can simply crouch and hold your breath. Doing so will immediately stop the water from flowing around you, allowing you to safely walk on land. However, if you're already swimming when you do this, you'll start to take damage from the water pressure and will eventually drown.

If you want to remove water from minecraft, you can use buckets to scoop it up and then empty it out elsewhere. You can also use a sponge to absorb water from an area, though this won't work if the water is too deep. Finally, you can place blocks of sand or gravel in water to slowly absorb it and reduce the level.