- sagitta
- sagittal
- sail fin
- saline
- SAM
- sawtoothed
- scad
- scale
- scalloped
- scapula
- scavenger
- school
- sciaenids
- scute
- seaweed
- sediment
- segment
- semipelagic
- sergestids
- sericeous
- serology
- serra
- serranids
- serrate
- serration
- sessile
- seston
- seta
- sete
- setiform
- setule
- sex
- sexual dichromatism
- sexual dimorphism
- Seychelles Islands
- shallow
- sheath
- shelf
- shell
- shrimps
- siganids
- silt
- sinuous
- sinus
- SIO
- skeleton
- SMF
- soft fin
- soft rays
- soil
- somatic
- somite
- SOSC
- spatulate
- spawn
- speciation
- species
- sperm
- spheroidal
- spicule
- spine
- spiracle
- sponges
- squamation
- squid
- stalk
- stellate
- stenohaline
- steroid
- sting
- stipe
- stock
- stomach
- stratification
- stria
- styliform
- sub-
- sub-Recent
- subadult
- subarctic
- subcutaneous
- subequal
- subgenus
- subhorizontal
- sublittoral
- suborbital
- suborder
- subphylum
- subpolar
- subspecies
- substrate
- subtropics
- subvertical
- sulcate
- sulcus
- superclass
- superior
- supermales
- superorder
- supra (as a prefix)
- supralateralis
- supralittoral
- supramaxilla
- supratemporal
- suture
- swamp
- symbiosis
- sympatric
- sympatric species
- symphysis
- synonym
- systematics