The Lander is a transport unit designed to carry two of any type of Ground units across the sea. Landers can be loaded and unloaded at shoals and Seaports.
Landers rely on other Naval Units, and sometimes Air Units for protection, as Landers carry no weapons and cannot fire on enemy units. Any units that are loaded onto a Lander are lost should it get destroyed before the units get dropped off, so exercise caution that this doesn't happen.
Landers can be produced at Seaports and cost 12,000G each. In Advance Wars: Days of Ruin, Landers cost only 10000G each to deploy.
As mentioned, Landers require support in order to survive, so protect them with other Naval and Air Units. Rockets can also protect Landers from a nearby shore if close enough.