i got to there forget all that happen but it has to do with makeing it to shore or something cuase he sinks the ship
have played all five levels, and the easiest way is indeed to jump ship after setting the explosive, swim to the shore, get behind a palm tree, take out the fully loaded RL, and when the chopper attacks, just keep circling the tree trunk, always keeping the chopper's machinegunner between you and the tree trunk. you will get plenty of opportunities to fire a rocket when the chopper's tailprop appears [when backing up] or his nose appears [peeks around the edge of your cover], then simply aim forward [or rearward] of the horizontal direction. when the chopper zooms up vertically, just forget about shooting, and focus on rapid circling to keep the cover/treetrunk between you and the chopper. i died a few times at first but by the time i got to the higher levels i could defeat the chopper before it defeated me. btw one of the great alltime classic shooters, just wish it had had a little more [human] eye candy to go with the great tropical scenery!