What annoys me is "mermaid tootles about on land in a wheelchair" is such an obvious concept – the whole thing where mermaids and mermen get legs automagically when they go on land is a specific bit linked to legends and stories that need the mermaid to pass when they're among humans.

But why couldn't a mermaid end up with a geas being placed upon her that forces her onto land in a setting where Our Mermaids Are Different and don't get automagical legs? Where she's forced to crawl out of the surf and build a rudimentary chair out of steering wheels and other washed up bits of wrecked ships before she even gets to questing properly.

There's enough metaphors and similes and symbolism there to drive a thousand stories, and a thousand more if you add in potential antagonist versions of that concept as well.

Yet it's never been done AFAIK!? wtf fantasy fiction?