Pacific Islands surf forecast

Pacific island reef passes are the purest expression of swell meeting bathymetry. There is no continental shelf to bleed energy, no river sediment to soften the bottom — swell arrives from deep ocean and meets coral that rises almost vertically, usually at a pass where water drains back out through a gap in the reef.

Teahupo'o is the extreme case: the reef comes up so abruptly that the wave has no room to shoal gradually, and the face draws water off the reef itself as it breaks. That is why it looks structurally different from any other wave, and why its face height bears so little relation to the offshore reading.