ORIGINAL: ncc1701e
This is time for the fleet to go back to Sena Gallica for resupply. I am ordering Sextus Pomponius to assume back command of the fleet. 5 days later, waiting for him, the fleet will be able to sail to Sena Gallica.
Time for the AI to play...
...
shouldn't need to send the fleet back. Usually a fleet carries far more supply than it needs so it becomes a floating depot (albeit one that can sink on you).
Hover over the supply symbol and it'll tell you if it has surplus supply.
What you can do is to send an empty supply wagon back out to the fleet, it'll draw on that surplus and then you can return it to the land - should take 3 turns for the round trip. Allows you to sustain a siege of a coastal city quite well - as long as you don't get hit by winter or have to fight.
More generally, keep your fleets in the defensive stance. Two reasons:
a) they don't lose cohesion very fast so can stay at sea longer;
b) if they fight, the defensive value far outweighs the attack value so you gain an advantage