Could a dragon be used at sea using a boat like an aircraft carrier? Unless they can fly straight across the narrow sea, that is the only way I can see the Stepstones falling to Daemon.

I suppose you could use a dragon to transport men, but why bother? It’s far more useful to use the dragon to burn your enemy’s fleet out of the water while Corlys Velaryon transports the men you’ll need to dislodge the island garrisons.