See the attached for the sketch.
This game is about swimming duck (or could be any other character) swim within two circles and enemy (whale or you can come up with any-other) try to catch the duck.
So this game is an escape the Hero from Enemy, Hero always swim in the two circle marks.
There are diamonds pop-up in the circle and duck/Hero need ...
Skills: graphic design, iphone app development, iphone ui design, adobe illustrator, adobe photoshop