When you start game, you need to select three difficulty: Easy, Normal, Hard.
Easy Mode : You can see bubbles which indicated there are a crab under it.
Mormal Mode : You can see nothing indicated where crabs are,but they just there,watch out and find out,use your memory.
Hard Mode : You can see no clue too,when fish catch by a crab, it will change it's hidden position randomly. Just count on your luck.
In Game, you will see a fish icon on Top right corner of the screen, click it once,one fish will be called,fish will find their own target,then take it back to the rock,when all photosphere be collected,you can go to next level.
There are crabs hidden under sea,if they feel the fish, they will catch them,small fish will be scared away.
You can use your left mouse button to guide small fish. Click Help icon on the left buttom of screen to get help.
Every photosphere collected can hatch out more fish,when you go to next level,you can see the number of the fish on upper left corner of the screen.