The best/easiest time to unlock this achievement is at the very beginning of the game when you first gain control of the diver/character. Use RT to dive and LS to swim down towards the sea floor. Once near the sea floor; start swimming upwards using LS while continuously pressing A to leap out of the water.
NOTE:
- This achievement can be unlocked at various locations throughout the game.
- Whether the character does a big or small leap out of the water will not matter, the achievement will still unlock.