What prevents transporting troops by (inland) sea?

Question

Earlier, I was able to invade Crete by sea from Morea (near Athens on the southern tip of Greece) with two infantry simply by selecting them and right-clicking on Crete as you would normally, I assume because I had a small fleet of three Galleys and three Cogs. It even showed them move first to the ships and then--after a short delay--onto Crete.

But now I've just conquered Venice and am trying to return home to Dalmatia via the Gulf of Venice. I have a large fleet in the gulf and control both provinces. When I select the army and right-click on Dalmatia, it makes sound like it will move but doesn't do anything.

There are a few things I suspect may be blocking the convoy:

1. The port is not actually adjacent to the gulf but on the sea below it. If this is the problem, do I need to split my fleet across both sea regions? Do both fleets need to have Cogs?

2. Venice has a fleet parked in a port adjacent to the gulf. Even though it appears I have them blockaded in the port, are they blocking the convoy?

3. I probably have more units in the army than Cogs in the fleet. Do I need to split up the army and move the stacks piecemeal?

Answer 1

Your answer 3 is correct.

You either need to have enough transport ships to move the entire stack at once or you need to split your army into chunks that fit onto the amount of transport ships you have.

If you have 19 troops and 15 transport ships, you will need to split your forces and send one batch of 15 or less across, then send the remainder.