Therefore you have to know when he is in the ocean and when he is not. The rest should be easy. To know that you somehow need to recognice where the ocean is. Maybe you can do it like in this examples: Gravity Engine Operation: Crash Test Or maybe there is an easyer way for doing that in your scenario. But therefore it would be very helpfull to know how your scenario is built up. (Do you use objects for the ocean?, Is there a scrolling world?...)

The whole map is water I want to know how can I make a the character swim. So when presses a he's swiming upward at a slow speed (less then 1)

I Need help FAST

For a smooth movement you just need to use double values instead of int values for the location of the players. If you have a look at the class Player in Operation: Crash Test you'll find what you need. Just use the class Player as the superclass and it should work.