Tender

A tender is one of several types of boat or ship, all sharing the general function of servicing another type of air or sea vessel.

seaplane tender - supplies and services seaplanes
submarine tender - resupplies submarines
motor torpedo boat tender - resupplies motor torpedo boats
ship's tender - used to transport people and supplies to and from a large ship

Steam locomotives often have tenderss, which are a type of railroad car hauled immediately after the locomotive proper that contain the fuel and water.

Legal tender is a term used of currency.