How useful are seaplane tenders compared with proper aircraft carriers?
Short answerA tender establishes a local seaplane base; a carrier moves air power with the fleet and is better suited to winning command of the sea.
NotesA seaplane tender can turn a sheltered bay or island into a temporary flying-boat base, for example by supporting PBY patrols. The aircraft disperse from that locality and return to the tender for fuel, maintenance, and supplies. A fleet carrier instead brings a mobile airfield with the battle fleet. The carrier helps gain command of the sea, while the tender extends control and surveillance from a chosen position.