I think its a nice MOC but there are a few things that could be improved
POSSIBLE IMPROVEMENTS
1. Ill start at the back of the raft and move forward, cocerning the area were the window and parrot are maybe you could add some SNOT tiles to the top of it, the studs just tend to stand out.
2. I'm not trying to be sarcastic but lets just think about this, Isnt it natural that when a ship goes down there is going to be debrie, and in this case there was a battle so there will be more debrie then usual, so if I were you I would add some barrels,snot tiles floating around, stuff like that.
3. The lady being attacked by the shark, she should proablly be facing the shark, and the guy in the box should proablly be facing the shark too.
4. Maybe you could add some white tiles around the shark, raft and the boxes to make it look like they are moving and cutting through the water.
5. The shark does look a little funny lying on the water, so I would suggest removing the tiles underneath of the shark and place some white and blue tiles around the edges of his body.
THINGS THAT I LIKE
1. The raft is great, simple but well done.
2. The pirate in the left box, His torso is awesome.
3. You have done a good job on the SNOT tiles.
Overall this is a great MOC, add a few of the suggestions above and you will have a possible winner. Good job Good Luck