What size boat requires a captain's licence, and what rules apply?

In Denmark, most privately used sailing yachts and displacement motorboats under 15 metres need no skipper's certificate, but qualifying planing motorboats and all personal watercraft require specific licences. Recreational vessels of 15 metres or more fall under a different certification regime; abroad, requirements also depend on the country, vessel registration and private or commercial use.

Check the boat's category

Start with where you plan to operate, whether the trip is private, and the boat's documented length, hull type and engine power. Length alone does not determine the qualification required. A small, powerful RIB can require one while a much larger sailing yacht does not.

For ordinary private boating in Denmark, the usual rules are:

• Sailing yacht under 15 metres: no compulsory skipper's certificate simply because you sail it.
• Displacement motorboat under 15 metres: generally no compulsory speedboat certificate, provided it does not fall within the planing-boat rules.
• Planing motorboat under 15 metres: a speedboat certificate may be compulsory, depending on length and engine power.
• Personal watercraft: a dedicated PWC certificate is required, whether you own or hire the craft.
• Recreational vessel from 15 metres to below 24 metres: skipper and potentially other crew qualifications apply, depending on the operating area and machinery.

At the 15-metre boundary, check the vessel's official measurement and the Danish Maritime Authority's requirements before buying or taking command. An advertised model length is not sufficient evidence.

The Danish speedboat rule

The boat must first be designed to plane. For planing boats from 4 metres to below 15 metres, the usual test is whether engine output in kilowatts exceeds the square of the boat's length in metres, plus three: kW > length × length + 3.

A 5-metre planing boat has a calculated threshold of 28 kW, approximately 38 hp. A 50 hp outboard exceeds that threshold, so the operator needs a speedboat certificate. A 7-metre planing boat with 150 hp also exceeds its calculated threshold of 52 kW, approximately 71 hp.

Boats under 4 metres have a separate power threshold. Do not apply that formula to a small tender. Use the Danish Maritime Authority's calculator with the documented length and engine output; for twin engines, use their combined power.

The operator must normally be at least 16 to operate a boat requiring the speedboat certificate. Slowing down does not remove the requirement. It depends on the boat's classification and installed power, rather than its speed on a particular trip.