It's an interesting idea, and doesn't require too much guidance to get started with... I did have to die a handful of times before I figured out what I needed to be doing, but once I did figure it out, it was easy to keep going. There could be a little more interactivity... for example, instead of making a bee line for the ship, maybe the sharks could go after the swimmers every now and then. Some sort of score system or progress bar would also be welcome.