Counter sterns, or cutaway sterns, are characterized by an upwardly curved profile, begining fore of the after perpendicular. Counter sterns are similar to cruiser sterns, however on counter sterns, the cutaway for the rudder occurs above the waterline, and consequentially the counter stern has a pronounced aft overhang and exposed skeg/rudder.
Counter sterns add deck space aft. The added height above the water line limits the amount of green water on this deck, and the enclosed space provides a measurable amount of reserve buoyancy. The lower hulls general ship-shape helps part a limited to moderate following sea. A larger rudder can be fitted within the "hole" underneath the counter for draught-limited vessels. The inclusion of a counter stern can also be seen as an aesthetic choice.
The raised deck space adds little to no buoyancy through the aft end, inducing an aft trimming moment. In moderate to heavy following seas, the sudden increase in buoyancy caused by the submergence of the counter stern can induce list, potentially exasperating any conditions of heel (such a vessel may broach).