Let’s face it, there’s a lot of words for different bodies of water. Lakes, reefs, gulfs, all that jazz. Someone should clear up the differences! There’s a post on Paths similar to this.
So, here's a totally not comprehensive guide to
backwater: water held or forced back, as by a dam, flood, or tide
bayou: any of various other often boggy, sluggish, stagnant, slow-moving or still bodies of water
bay: a body of water forming an indentation of the shoreline, larger than a cove but smaller than a gulf
brook: a small, natural stream of water
canal: a long narrow arm of the sea penetrating far inland
channel: a length of water wider than a strait, joining two larger areas of water
creek: a stream smaller than a river, sometimes in a marsh
cove: a small indentation in the shoreline of a sea
estuary: that part of the mouth or lower course of a river in which the river's current meets the sea's tide
fjord: a long, narrow arm of the sea bordered by steep cliffs: usually formed by glacial erosion
gorge: a chasm, especially one through which a stream runs
gulf: a portion of an ocean or sea partly enclosed by land
inlet: an indentation of a shoreline, usually long and narrow
lagoon: an area of shallow water separated from the sea by low sandy dunes
lake: a body of fresh or saltwater of considerable size, surrounded by land
pond: a body of water smaller than a lake
ria: a long, narrow inlet of a river that gradually decreases in depth from mouth to head
rill: between a rivulet and brook
river: a natural stream of water of fairly large size flowing in a definite course
rivulet: between a river and a stream
run: located near a stream or other small body of water
spring: a natural pool or stream of water coming up from the earth
sound: a narrow stretch of water forming connecting two wider areas of water that are not the same
strait: a narrow passage of water connecting two other large areas of water
stream: a body of water flowing in a channel or watercourse
sump: a pit, well, or the like in which water or other liquid is collected
torrent: a stream of water flowing with great rapidity and violence
whirlpool: water in swift, circular motion, as that produced by the meeting of opposing currents, often causing a downward spiralling action
As I said last time, I’m sure there’s a couple of words I missed here and there, but these are the majority of words you will need. Happy writing!