Undulating

To move in waves. Referring to the movement of a female fish’s tail in a waving motion used to move gravel for the construction of a redd.

Uni Knot

a knot used for terminal and line-to-line connections.

Upstream Fishing

facing, casting, and fishing upstream in flowing water, allowing the fly to drift back to the angler who is out-of-sight of a fish. Common practice of dry-fly anglers.

Upwelling

A rise in water from a lower level to a higher level, usually induced by current and wind.