FCDO advice including information on permitted duration of stay and visas for Denmark: www.gov.uk/foreign-travel-advice/denmark
For information on the validity of RYA certificates abroad see Evidence of Competence Abroad.
Evidence of competence is required for some powerboats under the Danish flag. The RYA has been advised that this requirement does not extend to foreign flagged boats.
For foreign flagged vessels, there is no specific requirement for evidence of competence other than that stipulated by the vessel's flag state.
EU member state (part of the customs territory of the EU (which includes territorial waters)). Further information is provided on the Entry & Exit Formalities page under Customs - EU Member States.
Part of the Schengen area.
As part of the customs territory of the EU (which includes territorial waters) and the Schengen area customs and immigration checks may not always be required on arrival and departure.
See Border control | Danish police (politi.dk) for further information.
See holding tanks for information on the discharge of waste water.