Spume

Spume - Foam, froth, frothy matter. 

From the Old French spume or the Middle English Spome. For example:

1440   Gesta Romanorum.   For all thing that are in the worlde are not but as a spume in the see.

PS. Just in case anyone is tempted to buy one of the new Peterhead flats, that I photographed yesterday, I have to confess that they were in reality a pile of fish boxes.