The slowest moving fish are the Seahorses moving at 0.001mph
Seahorses propel themselves by using a small fin on their back that flutters up to 35 times per second. Even smaller pectoral fins located near the back of the head are used for steering. They are normally seen swimming in pairs with their tails linked together, keeping them in line with each other as they swim so slowly. In comparision to the Seahorse, the fastest fish in the sea is the Sailfish at 68mph. Other faster fish in the sea include Marlin, Bluefish Tuna, Great Blue Shark and the Swordfish.
Image from www.flickr.com/photos/stuutje