In the UK this would be pretty much a non-starter for license reasons. Marine is also a band where illicit use rarely works because of the limited channels and the public nature.
You already have a marine radio in the boat I assume? I do know one guy locally who uses on of the UK hire channels that are just above marine band, and he removed his marine radio and swapped it for a multi-channel radio that he programmed the marine channels into, plus the extra one he uses to chat to home. It’s half legal, as he does have the ability to transmit on the hire channel, but he is using a non-type approved radio on marine band. However, as the display shows the usual channel numbers, not frequencies, I doubt anyone will notice. It just doesn’t have the new emergency buttons and data reporting - but loads of older real marine radios don’t either - his just has one extra channel that marine radios don’t.