(n.) the chain of bubbles left by an otter as it swims underwater
A chine is a trail of bubbles left by an otter as it swims beneath the surface of an area of water.
Yes, that word is genuine: the first volume of the English Dialect Dictionary defines it as “the small bubbles rising from an otter as he dives across the bottom of the water.”
The EDD also pinpoints this word to Northumberland, and suggests that etymologically it’s just a local corruption of chain. Lang-chines and short-chines are other Northumberland words for various types of farmyard equipment, while shoother-chines (literally, ‘shoulder-chains’) are the chains that link the panels of a yoke together.
While we’re on the subject of otters, incidentally, a few more from the HH archives: a group of otters is called a romp; an otter’s droppings are called its spraint; and in seventeenth century English, they were variously known as water-weasels, dog-fishers, and river-dogs. Just when they couldn’t get any better.