Undertow – A current below water surface flowing seaward; the receding water below the surface from waves breaking on a shelving beach.
Uni-knot – A popular basic knot or attaching line to hooks, swivels etc and can be used to join two lines together.
Uni-tech cast – A variation of the off the ground cast where the lead is laid out back towards the angler and inside the tip of the rod.
Uptider – a rod designed for uptide boat fishing with an extended handle below the reel seat to facilitate casting.
Uptiding – A type of boat fishing where the bait is cast uptide and away from the area around the anchor rope and boat. Grip leads are used and a belly is allowed to develop in the line after the rig settles. Bites from larger fish are normally slack liners. Originally developed in the shallow waters of the Thames estuary.