No matter what I've tried I can't execute a coastal assault - ie, land an army from a ship and attack a castle in the same turn. Even if the castle is right there on the coast, the army always just disembarks from the ship, chills for a turn and only on the next turn can it actually do anything.
What's worse, I've seen the AI actually do this successfully - land and attack in the same turn. Are my generals missing something? Some trait or ability?