Scyllaea fulva 
Sea Lemon 
Semicassis labiata 
Semicassis undulata 
Semper's Armina 
Shag-rug Nudibranch 
Shagreen 
Shireen's Phyllidiopsis 
Short-tailed ceratosoma 
Sky Blue Phyllidia 
Slender Roboastra 
Slug-like cowry 
Small Pointed Snail 
Smaragdia souverbiana 
Smooth Periwinkle 
Snipe's Bill 
Sohgenia palauensis 
Solar-powered phyllodesmium 
Solaropsis gibboni 
Sooty Seahare 
Sordid Moon Snail 
Spanish dancer 
Spanish slug 
Speckled periwinkle