Oh no I mostly agree with the sentiment! I wouldn't say complete crap, but you definitely get what you pay for. I think inappropriate in so far that you might be better with a mobile unit rather than an HT, and that you'd need to buy an aftermarket antennae to replace the rubbish it ships with. And probably illegal, I'd have to do some research on this particular model as I believe it's a newer one and they may have tightened up on the internal specs, and I don't know the UK Marine specs & requirements.
Some hams did research based on the UV-5R and found that some models were compliant and some were too emissive. Is that a word?
In my case it was ideal, the frequencies I use it on have no emissions requirements, it's a cheap HT with a backlight and it can handle me running through trenches and jumping on it all day! (Oh and the battery appears to last forever.)
I think in OPs case it would be worth spending a little more and getting something a little more reputable.