Chain catshark (Scyliorhinus retifer, public domain)

Catsharks (Scyliorhinidae) are the largest shark family. Many of the 160 species live in deep water and are rarely seen by divers. Their bodies are elongated. Two small spineless dorsal fins are set far back. Catsharks are most likely named for their oval eyes, that have a cat-like appearance. Catsharks range from 30 centimeters (12 inches) to 1.6 meters (5.2 feet) in length. They are not dangerous to divers.

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