first off, there's two variations:

the first, a sub AU called 'Voyagers' intended for SolHau (with a fem!Sol named Mahina) because i SHIP IT TOO MUCH AND I CAN'T LIVE WITHOUT IT- also has a sub AU without pkmn, where it more closely resembles the movie. we're talking about the irl-creatures-n-shiz sub-AU.

Voyagers!Hau kind of fills Maui's role...but:

1) Maui and Moana actually exist, so Hau sure as heck ain't Maui

2) he's like that one demigod who exists, but nobody ever really talks about him

So about Hau...

- he was neglected by his parents as a toddler, and before death could snatch him up, the gods took pity on him and made him into a lil demigod

- instead of a hook, he has an anchor that's comedically about half his size so he's constantly lugging it around

- his hair is actually curly...and he wears it down

- he can shapeshift but it's kinda limited. he can go common dolphin (not bottlenose, like a long-beaked common dolphin), dolphin-merman, albatross...

- he has one tattoo, and it wraps all along his left arm and ends on his pec

- the guardian (and future immortal chief) of Mahina's peeps...but he doesn't find them until she gets lost

- secretly depressed but hides it with his normal happy-go-lucky personality

- can barely sail himself

- likes making stupid-looking tikis out of wood and lining paths with them
-they definitely don't have names—

- literally weaved his own pants because he is appalled at idea of wearing leaves around his waist...tho he did it for the first few hundred years

so um...Mahina:

- Moana's great great great granddaughter (separated by four whole generations)

- not a v great sailor, but she tries

- teased about it because her grandma was a great sailor and she sure as heck ain't

- gets lost when they're exploring an island and meets Hau

- is smitten with him after the first like two minutes because he saves her from a big scary bear-like monster...and he's a pure cinnamon roll

- fascinated with the stars and the sky, constantly saying that she "belongs up there" to the immediate fear of her people

Maui might be an asshole...like once or twice, to Hau

There's definitely screaming- lots of screaming-

everything else can be explained in a oneshot