The most common shapes are called open-ended spanner and ring spanner. The term wrench is generally used for tools that turn non-fastening devices (e.g. tap wrench and pipe wrench), or may be used for a monkey wrench - an adjustable spanner. In North American English, wrench is the standard term.
The definition of first mate is the person on a boat that is second in charge after the captain. An example of first mate is the person who gives orders while the captain is busy. first mate. first mate.
Re: charging battery while its in the boat? It's how my batteries get charged. Carry the charger out to the boat, hook it up, plug it in. An on-board charger would be even more convenient, one with maintain mode you just plug it in & leave it.