Wiktionary
n. 1 (context obsolete English) a ship designed to tend to the needs of seaplanes, floatplanes and flying boats at sea, for resupply, refueling, sometimes including catapult launch 2 (context obsolete English) a type of aircraft carrier specialized in dealing with airplanes that can use water as a landing surface
Wikipedia
A seaplane tender is a boat or ship that supports the operation of seaplanes. Some of these vessels, the seaplane carriers could not only carry seaplanes but also provided all the facilities needed for their operation; these ships are regarded by some as the first aircraft carriers and appeared just before the First World War.
Usage examples of "seaplane tender".
Navy command ship bristling with radar antennas and other navigation and communications gear--six huge oceangoing tugs, five supply ships, a submarine mother ship, two tenders, two oilers, a small troop transport to accommodate the personnel who would work aboard the iceberg, a seaplane tender that had been converted into a floating laboratory and informationprocessing station, and a helicopter carrier with twelve personnel choppers and three huge transports with sixbladed counterrotating props capable of lifting twenty-five tons.
The new lead from the power box snaked smoothly down to the water and up the dark flank of the seaplane tender.
The seaplane tender nudged peacefully against the tire fenders of the dock while lines fed electricity from a shoreside outlet box over the boat's brass rail.