Breaking ocean waves on other planets possible? I have always wondered if there were an ocean on another planet with stronger or weaker gravity, would it be possible to have breaking waves?
 A: Breaking waves are understood as a breakdown in the solutions of the shallow wave equations. So yes there will be breaking waves on any world that has liquid seas with wind to generate waves big enough and shores where the sea becomes shallow. Stronger gravity would modify the speed and height of the waves but if the wind is strong enough and the oceans big enough for the wind to stir the waves up, then there should still be breaking waves.
A: Any planet that has liquid on its surface pretty much has to have some atmosphere, else the liquid would have evaporated and the gas diffused into space long ago.  It is hard to imagine a planet with a reasonable atmosphere not having wind.  Since all it takes is wind over liquid to make waves, which will be breaking if there is a sloping shore (also hard to imagine wouldn't be the case somewhere), I don't think you'd find a planet with at least pond-size liquid on its surface not having breaking waves.  The size and speed of propagation will differ with gravity, viscosity, and density of the liquid.
Note that here on Earth even small ponds with light wind have breaking waves.  They may only be a few mm high in that case, but if there are waves and some minimum slope to the shorline, there will be breaking waves.
