It would be nice if you add some stuff like a trap for fishes.
Or you could add some defense stuff against the shark , something like a spickes .
And i think after playing 1 hour its too easy to survive , so something like a dificulty would be nice too.
So like if you play easy there is only 1 Shark . If you play middle there are like 3 Sharks . And if you play Hard /Extreme there are 5< Sharks.