Shallowdraught

Shallowdraught (also spelled shallow draught or shallow-draft) describes vessels or hull designs with a relatively small vertical distance between the waterline and the keel. The draught determines the minimum water depth a vessel can safely navigate; shallowdraught craft are intended for areas where depth is limited, such as rivers, estuaries, coastal waters, lagoons, and reefs.

Design approaches to achieve a shallow draught include flat or nearly flat bottoms, wide beams, multihull configurations (catamarans, trimarans), reduced keel depth, and lightweight construction. Some specialized craft use lifting keels, retractable centerboards, or air-cushion systems to alter effective draught as needed. Hull shape and ballast arrangements are adjusted to maintain stability while minimizing immersion.

Advantages of shallowdraught vessels include access to restricted waterways, closer shore approaches, reduced need for dredging, and suitability for operations like river transport, ferry services, surveying, and certain military and rescue roles. Trade-offs commonly involve reduced seakeeping in heavy offshore conditions, increased sensitivity to wind and waves, lower maximum payloads relative to hull volume, and potential limitations on speed and directional stability.

Operators of shallowdraught craft must consider tidal ranges, navigational hazards, and accurate charting. The term is used in both commercial and recreational contexts and intersects with regulations, port infrastructure considerations, and vessel classification related to safe operating waters.