Sea State
The definition for the present condition or state of the sea.

Seal Skin
A really thick or heavy wet suit...usually 5mm or more.

Seams
Seams-The connecting area between panels on a suit; one of the most important zones and the focus for much of new developments in wetsuit technology. (See: flatstitched, blindstitched, double blindstitched, taped, stress point taping.)

Secondary swell
The second dominant swell at a specific location like a buoy.

Seine Waves
Deep water swells that are very well-approximated by pure sine waves. Steep - refers to angle or pitch of wave face. Waves formed close to the shore by local wind conditions, unorganized, tendency to be slop.

Section
A self-contained part of a breaking wave that breaks prematurely ahead of the original curl of the wave. The curl of a perfect wave will peel off without any sections. Obviously, most waves aren't perfect, but sections can create great opportunities for maneuvers like floaters or re-entries.

Seminar Gnar
A Dude that drops in on every wave just to show off to his crew.

Seshie
What a burnout surfer calls a surf session.

Set
A series of waves approaching the lineup. Waves almost always arrive in sets, and the periods in between sets are called lulls.

Setup
The general moniker used to describe a surf break. It includes ocean floor contour, land mass points, etc. Also used as a general description.

Sewer Surfer
A hodad or hodaddy who cruises around on Friday and Saturday nights with his board on top of his car to try to impress the chicks.

Sex Wax
An original and once the most popular brand of surf wax. 

Shack Up
To exist in a cohabitational arrangement, enjoying the benefits thereof, sans an official committment.

Shacked
To get tubed...barreled...spend time in the Green Room.

Shacka
Hawaiian Pidgin for "Right On." Also a common hand gesture used by making a fist and extending the thumb and pinky.
 
Shallows
Generally, water depth less than one-half the wavelength (distance between wave crests) of the waves is considered shallow water.