- Salt pan
- small dip in high meadows where water is stranded after the tide falls
- Saltmarsh
- transition area of salt tolerant plants between terrestrial and marine ecosystems that are occasionally flooded by high tides; high marsh in contrast to low marsh mudflat
- Sargassum
- species of brown algae that is primarily found in the Sargasso Sea
- Scavenger
- animal that feeds on dead plants and animals
- Scrape
- depression in the sand or substrate that some shorebirds birds create. The bird leans forward on its breast and scratches with its feet while rotating its body axis.
- SCUBA
- device that lets a diver breathe air while under water (letters stand for Self-Contained Underwater Breathing Apparatus
- Scyphozoa
- class of Cniderians that includes jellies with a medusa form; true jellies
- Sea
- subdivision of the ocean, a smaller and shallower body of water than the ocean; often semi-enclosed or marginal where between land and the ocean
- Seagrass
- collective name for vascular marine flowering plants that grow in shallow waters on soft substrate
- Seamount
- peaked, underwater mountain rising at least 1,000m (3,280ft) above the ocean floor
- Seaweed
- collective name for non-vascular, non-microscopic plants that usually contain chlorophyll; commonly called algae
- Secondary consumers
- carnivorous animals
- Sedentary
- remaining in one place
- Semidiurnal tide
- tide that has two high and two low waters in each tidal day
- Semiprecocial
- chicks hatch with eyes open, covered with down, and able to walk; but unlike fully precocial chicks, remain in or near the nest for several weeks
- Sessile
- permanently attached to a substrate
- Sexual dimorphism
- differences between males and females in external appearance or behavior
- Shellfish
- aquatic animal with a shell; includes mollusks and crustaceans
- Shute
- bony plate
- Siliceous
- containing silica
- Siphon
- tube or tube-like part of an animal through which air, food or water passes
- Slough
- swamp, bog, marsh or pond that is part of an inlet or backwater
- Solitary
- living singly except during breeding and/or raising young
- Spawn
- to produce and deposit eggs
- Species
- distinctive group of organisms that can successfully interbreed and produce viable offspring
- Species diversity
- numbers of different species and their relative abundance in a given area
- Spermatophore
- capsule enclosing a packet of sperm produced by males of some animals that is directly transferred to the reproductive part of a famale's body
- Spiracle
- dorsal openings in the head region of some cartilaginous fishes through which water is drawn and passed over the gills
- Spiracles
- openings that allow entrance, passage, or exit of a gas or vapor, esp. of air
- Statocyst
- specialized sacs or organs on the rim of the bell and tentacle bases of jellies that assist animal in maintaining balance in the water column by sensing the pull of gravity; balance organ
- Stipe
- stem-like part of a kelp plant that connects the holdfast to the blades
- Stipe
- stem-like part of a kelp plant that connects the holdfast to the blades
- Strobilia
- multi-organism columnar pancake-like of very small jellies produced by a polyp; as jellies break off, the polyp is said to be 'strobilating'
- Strobilization
- budding: asexual transformation into reproductive process
- Sublittoral (subtidal) zone
- benthic zone from the low tide mark to the outer edge of the continental shelf
- Subsistence
- barest means needed to sustain life
- Subspecies
- a genetically distinct geographical subunit of a species. Also called race.
- Substrate
- any surface on which a plant or animal lives or on which a material sticks
- Subtidal
- below the intertidal, or below the level of the lowest tide. Also called sublittorial.
- Supralittoral zone
- narrow benthic zone on shores above high water mark that only becomes wet when there are storms or spray
- Surfline
- area near shore where the waves break
- Surge
- movement of a mass of water
- Surge channel
- channel along the edge of rocks or reefs in which the water level fluctuates with wave or tidal action
- Suspension-feeder
- an animal that filters out debris, detritus, or other particles suspended in the surrounding water
- Suspension-feeder
- an animal that filters out debris, detritus, or other particles suspended in the surrounding water
- Sustenance
- nourishment; that which sustains life
- Swell
- a large ocean wave that moves steadily without breaking
- Swim bladder
- gas-filled bladder of a fish that helps it maintain its position in the water column
- Symbiosis
- close relationship between two organisms of different species that is often of mutual benefit
