Most trips need an international flight plus a domestic connection, Malé, Sorong, Hurghada, Cabo, San Cristóbal. Allow a buffer day and book the domestic leg with generous baggage.
Very few liveaboards depart from a city you can fly into directly
The typical route is a long-haul flight to a national hub, then a domestic connection to the port town, then a short transfer to the marina.
Common patterns: the Maldives means Malé, then a domestic or seaplane transfer to the atoll if the boat is not in the capital. Raja Ampat means Jakarta or Makassar, then Sorong, then a harbour transfer. Egypt means Cairo or a direct charter to Hurghada or Marsa Alam. Galápagos means Quito or Guayaquil, then Baltra or San Cristóbal. Socorro means Cabo San Lucas by way of Mexico City or a US hub.
Two things to plan carefully
First, the domestic leg almost always has a lower checked-baggage allowance than your international ticket, sometimes as low as 15 kg — check that number and pre-purchase extra weight online. Second, book the international and domestic legs on a single ticket where possible, so a delay on the first leg makes the airline responsible for rebooking the second.
Airport transfers are included by many operators and offered as an add-on by the rest. Confirm which applies to your booking, and give the operator your flight numbers so they can adjust to delays.