- Saber-Toothed Blenny
- Sabertooth Fish
- Sablefish
- Sailfish
- Sailfin Blenny
- Sailfin Goby
- Sailfin Snapper
- Sailfin Tang
- Salmon
- Salmon Shark
- Sand Bass
- Sand Crab
- Sand Dab
- Sand Dollar
- Sand Eel
- Sand Flathead
- Sand Goby
- Sand Lance
- Sand Perch
- Sand Piper (marine feeder bird)
- Sand Sole
- Sand Tiger Shark
- Sandbar Shark
- Sandy Sprat
- Sarcastic Fringehead
- Sawfish
- Sawtooth Eel
- Scalloped Hammerhead Shark
- Scallop
- Scaly Dragonfish
- Scalyfin Fish
- Scarlet Cleaner Shrimp
- Scissor-Tail Sergeant Fish
- Scorpionfish
- Sculpin
- Sea Anemone
- Sea Apple
- Sea Bass
- Sea Blubber (Jellyfish species)
- Sea Bunny (Nudibranch species)
- Sea Cucumber
- Sea Devil (Anglerfish species)
- Sea Dragon
- Sea Fan
- Sea Hare
- Sea Lamprey
- Sea Lettuce (Marine Algae)
- Sea Lion
- Sea Nettle (Jellyfish species)
- Sea Otter
- Sea Pen
- Sea Pig
- Sea Raven
- Sea Robin
- Sea Scorpion
- Sea Slug
- Sea Snail
- Sea Spider
- Sea Squirt
- Sea Star (Starfish)
- Sea Turtle
- Sea Urchin
- Seahorse
- Sebastolobus (Thornyhead Rockfish)
- Sennet Barracuda
- Sergeant Major Fish
- Seven-Gilled Shark
- Shad
- Shark
- Sharknose Goby
- Sheepshead Fish
- Sheepshead Minnow
- Shortfin Mako Shark
- Shortnose Batfish
- Shrimp
- Silver Arowana (brackish species)
- Silver Carp
- Silver Drummer
- Silver Eel
- Silver Scabbardfish
- Silver Shark
- Silver Sprat
- Silverside Fish
- Six-Gilled Shark
- Skate Fish
- Skipjack Tuna
- Slender Filefish
- Slipper Lobster
- Slithering Eel
- Slender Snipe Eel
- Smalltooth Sawfish
- Smelt
- Smooth Dogfish Shark
- Smooth Hammerhead Shark
- Smooth Trunkfish
- Snaggletooth Shark
- Snapping Shrimp
- Snowflake Eel
- Sockeye Salmon
- Softshell Clam
- Sole Fish
- Southern Bottlenose Whale
- Southern Flounder
- Southern Stingray
- Spadefish
- Spanish Dancer (Sea Slug)
- Spanish Hogfish
- Spanish Mackerel
- Spawning Herring
- Speckled Moray Eel
- Spectacled Filefish
- Spider Crab
- Spiny Dogfish Shark
- Spiny Lobster
- Spiny Pufferfish
- Spiny Seahorse
- Spinyfin Fish
- Spinyhead Sculpin
- Spinytail Skate
- Splitfin Flashlightfish
- Spookfish
- Spotted Eagle Ray
- Spotted Garden Eel
- Spotted Handfish
- Spotted Moray Eel
- Spotted Pufferfish
- Spotted Ratfish
- Spotted Seahorse
- Spotted Wobbegong Shark
- Squat Lobster
- Squid
- Stargazer Fish
- Starry Flounder
- Starry Pufferfish
- Starry Skate
- Starry Smoothhound Shark
- Steephead Parrotfish
- Stingray
- Stippled Gunnel
- Stone Crab
- Stonefish
- Stout Beardfish
- Striped Bass
- Striped Bonito
- Striped Catfish
- Striped Eel Catfish
- Striped Marlin
- Striped Raphael Catfish (brackish species)
- Striped Seaperch
- Striped Surgeonfish
- Subantarctic Fur Seal
- Sugar Wrasse
- Sunfish (Mola Mola)
- Sunset Wrasse
- Surf Perch
- Surgeonfish
- Swallowtail Seaperch
- Swallowtail Shiner
- Swordfish
- Symmetrical Goatfish
