Gnarly
From Openwaterpedia
adjective - Gnarly can be difficult, dangerous, challenging, or large waves or rough water or froggy conditions in the marine environment when waves, surface chop, currents, tidal flows, wind, lightning, fog, or cold weather causes open bodies of water to become rough, disturbed, wavy, choppy, cold(er) or turbulent.
Usage
When returning to shore, the large waves were gnarly.
