A personal watercraft is a small, powerful and planing vessel that requires competences to operate. That is why you must have a certificate for operating a Danish personal watercraft.
You must be 16 years old to get a certificate for operating personal watercraft, and the certificate must be carried when at sea.

You can find out how to qualify for a personal watercraft certificate here​.​.

As a general rule, it is prohibited to use personal watercraft/jet skis closer to the coast than 300 metres. Within the 300-metre zone, it is only permitted to use these vessels perpendicularly to the coast at a speed below 5 knots. It is prohibited to use personal watercraft/jet skis in nature reserves, conservation areas and wildlife reserves. Read more (in Danish) on the website of the Danish Environmental Protection Agency under the headline "On the sea" and in the order on operation of personal watercraft issued by the Ministry of Environment and Food of Denmark (in Danish).

A blood alcohol content of 0.5 promille applies in connection with the use of personal watercraft and jet skis.

A life jacket or swim jacket must be available for everybody on the personal watercraft. Read more about swim jackets and life jackets (in Danish).

The regulations for preventing collisions at sea also apply to personal watercraft. This means, inter alia, that you must proceed at a "safe speed" in consideration of foreseeability and traffic density as well as rowers and swimmers.

You have a duty to give way to traffic from the starboard side and you have an unconditional duty to give way to sailboats and rowboats. If you have the duty to give way, you must do so in good time so that the other vessels can see that you are giving way. It is important to show consideration and good seamanship to other vessels and to observe one's duty to give way so as to avoid that a trip to sea ends in an accident.

When the sun sets, a personal watercraft also has a duty to carry lights: Green to starboard, red to port side and white to the back. Read more about the regulations for preventing collisions at sea (in Danish).

It is important to familiarize oneself with local navigational regulations. They are available from the website of the Danish police (in Danish) under each region. There can also be navigational regulations applicable to individual ports. In some areas, it is perhaps prohibited to operate personal watercraft, such as in the Port of Copenhagen, and in some areas there are perhaps speed limitations. See the website of the Danish Port Pilot.