A support vessel is a commercially classed yacht in its own right, usually 35 to 80 metres, that carries the equipment a superyacht has outgrown its garage for: tenders, toys, a helicopter, a submarine, and the crew to run them. Unlike a chase boat it is built and crewed for ocean transits, repositioning in convoy with the mothership.
The sub-categories are shadow yachts, helicopter support vessels, submarine support vessels and expedition support yachts. The support vessels pillar covers where the boundary sits against a large chase boat.