Large crosswaves like the ones below are very rare and often dangerous to swimmers and shipping alike. They are formed by wave production far out to sea. Usually, but not always, by different and geographically displaced weather systems.
The ones I have seen appeared in tidal pools with incoming waves from the sea and a perpendicular crosswind.
They have a beautiful symmetry to them.
Sipped from here:
By Michel Griffon , CC BY 3.0, Link
