This trophy is earned in
Chapter 14: Cruisin' for a Bruisin'After defeating the heavily armoured enemy that has a PAK-80 and then killing the wave of new enemies that spawn in, you will need to tap
on a large red sliding door. Once you enter the area behind the red door, a pool will be immediately in front of you.
Simply jump into this pool, wait for Drake to call out "Marco" and this trophy will be yours.