No pun intended - Mermaids (or mermen if that is a thing ... and at least my t9 or whatever word correction program seems to think that word exists) do need water. Now depending on what myth you believe in ... you may see them as something beautiful ... something that you may want to be with.
Let me start with how the movie starts (and I don't necessarily mean Tom Arnold, who can be annoying or super funny depending on your liking) ... it is the mermaid that is popping up ... and it is anything but a beautiful half woman, half fish kind of thing. Now Florida Man is a thing - and if you believe in that or know it ... you may also be in tune with the main character. Because he also can be annoying ... he is quite irresponsible ... and he is mostly on drugs.
These are just some of his issues. Social he is not - he is more into fish. Yes you probably have guessed where this is going ... still you probably haven't entirely (but why? But how? - I always remember that saying/joke regarding Mermaids from my English teacher - to teach us how to pronounce the words) ... if you think he acts completely ... crazy ... well you would be right (and he is wrong) ... on the other hand? What do we know? And also we wouldn't have a movie otherwise ... the "Psycho" scene by the way is something to behold ... although I reckon one could also compare it to Weekend at Bernies .... there are other nods to other horror movies or movies in general for sure.
All that said, just dive in - even if we stay on land most of the time ... and enjoy the show - yes another pun! Bon Appetit.