Effects of swell on sailing

[Amulet]

But ocean swells have wavelengths of 100s of metres. It's the ocean swell going into shallow water that makes the Bay of Biscay so unpleasant. Continental shelves are (by definition) less than 500m deep , and it shallows from thousands of metres deep over a short distance.

Aha - thank you. Seems wavelength is typically about 600 metres.