When you get the Key, turn around and swim back. Once you pass through the rocks, surface and locate the small ledge, where you can climb out exactly ahead. Climb on this ledge, then on the upper one and pick up the Small Medi Pack.

These are the same pick-ups, but from another view.

Jump into the water and swim to the other side past the small sandy island. There is a small outcrop beyond that you can climb on. To do that use the ledge of the rock having the shore and the bamboo hut to your back. Climb on it and pick up another Small Medi Pack.

Secret - From the rock you got the Medi Pack, turn so that the shore and the bamboo hut are to your back. Take a look across the water and notice the slope and the flat ledge next to it on the right hand side. Walk to the front right corner and take a running jump to grab the slope. Shimmy to the right and pull up on the flat ledge.

Turn right and take a diagonal standing jump to the next flat ledge on the left hand side. From there take a running jump to grab the next ledge. Pull up and pick up the MP5 Clips.