We are pleased to confirm that provided all the details you gave us remain unaltered and, most importantly, that your craft remains UK registered (or if your craft is not registered you must be a resident of the UK) then your policy and cover will remain unaltered. Please check your policy online.
Here are some useful links which may provide more information about keeping your vessel in Europe :
https://www.rya.org.uk/knowledge-advice/current-affairs/Pages/Brexit.aspx
https://www.pbo.co.uk/news/brexit-for-boat-owners-expert-advice-updated-66341
https://www.gov.uk/register-a-boat/the-uk-ship-register
https://www.gov.uk/transition