Your Health or Life in hungry shark evolution is shown by the green bar at the top right of the screen. Your health bar is constantly going down - think of it more as Energy. As you swim around you use more and more energy, and the best way to replenish that is to eat something. There are certain things which can also damage your health, should you collide with them or try to eat them. These include creatures of the deep like Jellyfish and hammerhead Sharks. You can also be attacked by other, aggressive animals, like Sting Rays, other Sharks or Puffer Fish.
Another way for your health to begin going down is if you dive down too deep in the ocean. This is because once any creature reaches a certain depth, the pressure of all that water above them begins to get painful. If you go too deep, you will be squashed. There are also unexploded military mines in the sea which you should do your best to steer clear of, as these will explode and hurt your shark. Finally, keep an eye out for the rare appearances of marauding submarines - these will attack you with their nasty torpedoes, which seems like a bit of an over-reaction, but there you go.
If you have a high enough levelled species of shark, you will be able to eat things like pufferfish. You can also eat submarines.
[spoiler][/spoiler] the shark vortex doesn't switch you to another place it brings everything around you to you [quote][/quote] your ugly