I remember watching a program on the
Polynesian settlement of the Pacific Islands.
The canoe paddlers had wave charts which were
used to navigate. The means by which the
waves were felt when very slight and the
means of discerning the cross waves which
told the navigators where they were on the
chart sort of in the Y direction was by the
pressure on the scrotum while they sat on
Perhaps it's not all bollocks, however much
dipping may be.