I like this game! I defeated Cthulu :), I like the fact that you can see the ground due to thunder, but majority of the time I am just looking at the radar :P.
The fact that you utilize "a speaker" to lure in the enemies is quite interesting, I lagged a bunch when I go close to cthulu, but thats expected from a browser. Good job overall! I do wish the controls for the boat were a bit better and the "space" catching of treasure is faster :P