Sea Slug
Pilgrim hervia (Cratena peregrina)
“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).
This supplemental online resource accompanies the book Scuba Diving Hand Signals by Lars Behnke, available on
Amazon.