The different levels are not difficult, although the points will depend on the time you take to pass the level, so you'll have to hurry up to get more points and discover new oceanic caves. In each level you'll have to complete some missions special missions: find some lost treasures. Those treasures will be indicated by an arrow, so you only have to follow the indications of the arrows to get them.
As you can imagine, you won't be alone in the ocean, you'll have to dribble lots of obstacles and enemies. The underwater world of Shark Attack is populated by balloon fishes, octopus, squids... and they'll try to stop and kill you but you'll also be able to use some of them to move in the water in a better way.
Oh! Don't forget you'll be diving, so you'll have to have an eye on the oxygen of your oxygen cylinder, you know what will happen to the diver in case the oxygen runs out.