A chase boat captain is the crew member who runs a superyacht's chase boat as an independent vessel: navigating, operating and maintaining it away from the mothership, typically with a Yachtmaster Offshore or commercial small-craft licence and a deckhand seconded from the yacht.
Because a chase boat travels under its own power rather than living in the garage, it needs at least one permanent operator, which is part of why the asset only makes sense on a real mission. The tender crew training and licensing guide covers the qualification stack.