- sail fin
- saline
- SAM
- sawback
- sawtoothed
- scale
- scalloped
- scapula
- school
- scute
- seals
- seaweed
- semi-imbricated
- semipelagic
- serrate
- serrations
- sessile
- sete
- setiform
- sex
- sexual dimorphism
- Seychelles Islands
- shallow
- sheath
- shelf
- shell
- shoaling
- shoulder
- shrimps
- sinuous
- SIO
- SMF
- snout
- SOSC
- spatulate
- spawn
- species
- spine
- spiracle
- Spitzbergen
- sponges
- squamation
- squid
- starfish
- stellate
- stenohaline
- stratification
- stylephorus
- subadults
- subcutaneous
- subequal
- subgenus
- sublittoral
- subocular pocket
- suborbital
- suborder
- subphylum
- subpolar
- subspecies
- substrate
- subterminal
- subtropics
- subvertical
- superclass
- superior
- supermales
- superorder
- supra (as a prefix)
- supralateralis
- supralittoral
- supramaxilla
- supratemporal
- swim bladder
- symbiosis
- sympatric species
- symphyseal groove
- symphysis
- synonym