Water flounder : The windowpane (Pleuronectes maculatus).

Example:


Taxonomy
fish, jetty, inlet, Flounder fishing, fishing, beach, anglers, groin, bait, tide, rocks, live bait, the surf, boat, baitfish, shore, spots, runnels.

Defination from the web:
Flounder are an abundant fish, but they aren't stacked like cordwood everywhere on the bottom. Here's how to zero in on the best cover and structure to fish. ... This flounder trip is probably typical of the majority of anglers on the water or fishing from shore. ...