Overview
Placer ( or pracel) is a term used by Portuguese and Spanish navigators and cartographers to refer to a certain kind of submerged bank or reef. Commonly the bottom of such a reef is sandy, but there are some where the bottom is muddy or stoney. Although most reefs designated as placer are flat and shallow, exceptionally there are some that do not share those characteristics and are known as placer acantilado. A placer usually provides an anchorage for seagoing vessels.
Etymology
The word placer derives from the Spanish placer, meaning shoal or alluvial/sand deposit, from plassa (place) from Medieval Latin placea (place) the origin word for "place" and "plaza" in English. The word in Spanish is thus derived from placea and refers directly to an alluvial or glacial deposit of sand or gravel.
Spanish navigator and explorer Pedro Sarmiento de Gamboa commented that placer likely originated as a term derived from placer mining in the Antilles, where pearl fishing was done mostly on shallow sandy reefs, which were compared to the sandy grounds in rivers where gold nuggets were found.
Since the word Placer in Spanish means 'pleasure', according to 16th century scientist Juan Pérez de Moya a placer is every dangerous submerged shallow bank. Moya claims that the landforms that received this denomination did so in an ironical manner, for it would be everything but a pleasure to navigate those treacherous waters under the constant risk of running aground.
However, other navigators contradict Moya by claiming that such a shallow ground would provide mariners with a much welcome anchorage after a long open sea journey, for in some placeres the waters are not as rough as in the open seas.
From Wikipedia (CC BY-SA 4.0).