Gozo and Comino look close on a map, but the transport is a separate booking. Gozo Channel does not call at Comino. Neither does the passenger fast-ferry route from Valletta, Sliema or Buġibba to Mġarr.
Book the return before the outward trip
Visit Gozo describes small ferries and water taxis from Mġarr Harbour to Comino, a short crossing. Operators may arrive at the Blue Lagoon or another landing, and the return point and final boat should be clear before you leave Gozo.
One Mġarr–Comino operator publishes its own schedule and ticket options. That schedule is not part of the six Malta/Gozo commuter routes on the FreeMalta ferry desk. Sea conditions can change a small-boat service, so confirm directly on your travel date. If you also need a Malta–Gozo crossing, plan its return separately.