A semi-displacement hull, in the context of boat or ship design, is a type of hull that blends the design features of a full displacement hull and a planing hull. With attributes from both these types, a semi-displacement hull is intended to travel faster than a displacement hull while still maintaining better fuel efficiency and a smoother ride than a planing hull. A semi-displacement hull retains the deeper 'V' shape forefoot of a displacement hull for smoother handling in rough water. However, it flattens towards the stern, similar to a planing hull, which allows the boat to partly lift out of the water at higher speeds. This feature reduces the hull's drag significantly, enabling speeds faster than a typically displacement hull while retaining more stability and seakeeping ability than a planing hull. This type of hull is often used for motor yachts, passenger ferries, pilot boats, and other vessels that require a balance between speed, comfort, and efficiency. Please note that the specific design of a semi-displacement hull can vary greatly, depending on the intended use of the boat, the desired balance between speed and stability, and the designer's preferences, among other factors.

1. Semi-displacement Hull Yacht: This type of yacht is designed with a hull that bridges the gap between full displacement and planing hull designs. It's designed to offer higher speeds than a full-displacement yacht but with greater fuel efficiency than a planing hull vessel. 2. Semi-displacement Motor Boat: A motorboat with a semi-displacement hull can navigate both calm and rough waters effectively. It can offer speed without compromising the stability and fuel-efficiency. 3. Semi-displacement Trawler: A trawler with a semi-displacement hull is an ideal option for deep sea fishing, which combines the speed of a planing hull with the sea-keeping abilities of a displacement hull. 4. Semi-displacement Power Catamaran: The semi-displacement hull of a power catamaran provides the vessel with speed and stability, allowing for efficient cruising at medium speeds. 5. Semi-displacement Superyacht: Superyachts equipped with semi-displacement hulls provide higher cruising speeds than full displacement hulls, but still possess the benefits of stability and fuel efficiency which enhance comfort for long voyages.

Fun Fact: Semi-displacement hulls are engineered to provide the best of both displacement and planning hull designs! They can maintain higher speeds than typical displacement hulls while still providing a relatively smooth ride in rough water. And an added bonus - they offer better fuel efficiency at slower speeds compared to planing hulls. They can literally make a boat operate like a sports car on the water! This is why they are commonly used in motor yachts and other types of power boats. They truly represent an innovation in naval architecture!