Two understandings are associated with the term boat lift. Ship lifts, caisson locks, and similar boat lifts have been used in commercial shipping lanes and deep sea ports since late in the 18th century. Locks and similar large-scale lifts are used to move boats between two bodies of water with differing levels. Today, the modern understanding of a boat lift, sometimes referred to as a boat hoist, is understood to reference a common piece of mooring equipment used for small boats and personal watercraft. Also known as portable boat lifts because the lift can be removed and reinstalled at another location, these modern mechanisms come in many forms and designs including freestanding or floating, as well as manual, electric, or hydraulic.
Modern boat lifts are used to lift and hold a boat out of either salt or fresh water. Most often, a boat is driven over straps, beams, a platform, or other mechanisms that sit at or just below the water level. Once in place, the boat lift allows boat owners, maintenance personnel, or dock employees to raise a boat out of the water for storage, repairs, or removal to a boat trailer for transport. Lifts eliminate the need for boat ramps to launch and remove boats from the water, since the lifting mechanism does the work of a ramp without the need for an additional vehicle with an attached trailer. Certain types of boat lifts, most often seen in floating set ups, require no actual lifting mechanism, but rather allow a boat operator to drive a boat up and out of the water directly.
Construction and features vary greatly among dock accessories like lifts and hoists, depending on manufacturer design and where the equipment will be used. Privately owned docks may have small galvanized metal boat lifts with motorized or manual crank mechanisms featuring ropes or chains to hold the boat around the hull. Commercial docks typically have large hydraulic boat lifts with cradles to accommodate larger, heavier boats. Boats hoisted out of the water may remain in the lift for storage at private docks, or in the case of commercial docks, used to lift a boat out of the water and move it to dry storage.
No matter the intended location, both freestanding and floating boat lifts are installed along piers or docks. Close proximity to a pier or dock allows the operator to drive the boat from the water into the lift, then exit the boat. Freestanding boat lifts are attached to legs driven into the seabed, lake bed, or other ground below the water's surface. Such lifts are not in any way anchored to the adjacent pier or dock. Alternatively, floating boat lifts have no legs, instead they are tied to a point on the shoreline, the adjacent pier or dock, or other stable point to prevent drifting while still allowing an operator to exit the boat on foot.