Bathymetry

In the great, early, 70’s, surf movie Big Wednesday, the film shows its provenance when the voice-over gravely intones that, “No one knew from where the big swells came.” Well, we all know now. Modern forecasting and modern understandings of storms, fetches, and swell generation means the old-fashioned, mysto swell is very much a historical relic.

But still, there does seem some magical, mystical X-factor which makes swells behave in strange ways — pump in some spots open to the swell and be close to non-existent in others of similar aspect. There are swells that do weird things, unexpected things, and not just on the east coast of Australia but in Indonesia, the Pacific Islands, Western Australia, Vicco, Europe, and elsewhere.

While it’s not always the case, quite often the key to understanding this mysterious behaviour of a swell once it’s generated lies with the black arts of Bathymetry. Let’s take a little stroll through this magical world and see if we can decode a few of the strange signals of the sea floor.

First, a definition is in order. Bathymetry is the study of the underwater depth of the ocean floor. For our purposes