The whales in the ocean go spout, spout, spout (put hands on head and then "spout" into the air)
The crabs in the ocean go pinch, pinch, pinch (only if you're sure your audience won't pinch each other!)
The dolphins in the ocean go leap, leap, leap (have to have an old enough group to all leap in the same direction. This is very important)
The fish in the ocean go wiggle, wiggle, wiggle (put hands together and wiggle your whole body)
The shark in the ocean goes chomp, chomp, chomp (make a giant mouth with both arms and open and close them)

Source: http://storytimeextras.blogspot.com/2012/02/wheels-on-bus.html