Providing armour support for the initial wave of assault troops was a critical concern for Sea Lion planners, and much effort was devoted to finding practical ways of rapidly getting tanks onto the invasion beaches in support of the first echelon. Though the Type A barges could disembark several medium tanks onto an open beach, this could be accomplished only once the tide had fallen further and the barges were firmly grounded along their full length; otherwise a leading tank might topple off an unsteady ramp and block those behind from deployment. The time needed for assembling the external ramps also meant that both the tanks and the ramp assembly crews would be exposed to close-quarter enemy fire for a considerable time. A safer and faster method was needed and the Germans eventually settled on providing some tanks with floats and making others fully submersible. It was nevertheless recognised that a high proportion of these specialised tanks might be expected not to make it off the beach.