Sea Slug

Hermissenda crossicornis (Jerry Kirkhart / CC BY)

“Sea slug” is the common name for a heterogeneous group of saltwater snails without external shells. The name is applied to members of the clades Nudibranchia (a prominent group of colorful gastropods), Sacoglossa (sap-sucking sea slugs), and Aplysiomorpha (large animals with small, proteinaceous internal shells).

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