When an army attempts to cross the sea, a transport ship is automatically supplied to provide passage. While these ships are similar to military vessels, they are slower, more cumbersome and are unable to withstand sustained damage. With that in mind, transport ships require the protection of your fleets if they are to transport large armies across the sea. Selecting a fleet and right-clicking on a transport provides an armed escort for the journey: any attacks on the transport will have to face the fleet first. To disembark an army or agent onto land, select its transport ship and right-click on the coast.