Encyclopedias, Almanacs, Transcripts, and Maps
- SDLP
- SDP
- sea cow
- Sea Level Change
- Sea Shepherd Conservation Society
- Sea Turtles
- Seabed Disposal
- Seabrook Nuclear Reactor
- seafloor
- Seals and Sea Lions
- Sears, Paul Bigelow (1891 – 1990) American Ecologist and Conservationist
- Seasonal Ceremonies
- Seattle, Noah (1786 – 1866) Duwamish Chief
- Seaturtles (Cheloniidae)
- Secchi Disk
- Secernentea (Secernenteans)
- Second World
- Secondary Recovery Technique
- Secondary Standards
- Secret Societies