With the strong focus on underwater and general marine operations in ARMA 3, we badly need a a staging platform for any kind of marine operations.
An amphibious assault ship could be one element, a LPD could be another option and finally a full scale submarine could be a great addition for the divers and SDV's.
This feature would make the new marine features a more interesting addition.
-Landing Platform, Helicopter (LPH)
-Landing platform/dock (LPD)