When it comes to power boats, the shape and displacement of the hull make a huge impact on its ocean abilities.  Most production power boats have a fairly flat-V hull shape that help it to easily get on plain in light seas.  This makes for great coastal cruising and island hopping.  Because they are designed to be up on plain, they are light yachts and are designed to bob above the water like a cork.  Blue-water cruisers have a hull shape that is designed for pushing water along the hull rather than bobbing on top of it.  With a deeper V-shaped hull, larger displacement and taller freeboard (the distance from the waterline to the deck), they are designed to slice through the water, which makes for a smoother ride offshore (anyone who has been on a production yacht on plain in rough seas know the feeling of slamming into a wave while on plain when the seas are too rough).

Production motor yachts are designed to be light and fast, so they usually have smaller tankage.  Blue-water cruisers are designed to cross oceans without needing to fill up their water or fuel tanks.  Production boats are designed for weekend, coastal, and island cruising.  They are meant to be light displacement boats made with lighter construction materials (more composites and laminates) so that they can get you quickly from place to place.  Blue-water cruisers are designed to be bulky and sturdy and are made with solid woods and thicker fiberglass.

Blue water cruisers are often single-screw yachts with fuel efficient engines that burn low amounts of fuel while traveling at an average cruising speed of about 6-10 knots.  One of the most important aspects of a blue-water yacht is a stabilizer system.  There are several forms of stabilization ranging from wings off of the sides of the yacht with wing anchors hanging down into the water to hydraulic fin stabilizers under the hull.  A stabilizer system helps to counteract the rolling motion of a yacht riding waves, making for a smoother ride in choppy and rough seas.