Seahorse (Laszlo Ilyes / CC BY)

Seahorses (Hippocampus sp.) share many features with the closely related group of pipefish. They have slender to stout bodies, flexible necks, and elongated snouts. Their skin is stretched over bony rings. Seahorses do not have scales. They range from 0.5 centimeters (0.2 inches, Severns' pygmy seahorse) to 30 centimeters (11.8 inches, spotted seahorse) in length. Like pipefish they are poor swimmers. The dwarf seahorse (Hippocampus zosterae) is the slowest-swimming fish in the world, reaching a top speed of about 1.5 meters (5 feet) per hour.

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This supplemental online resource accompanies the book Scuba Diving Hand Signals by Lars Behnke, available on Amazon.