TL;DR You could change the description to: "A man with amnesia who believes himself to be a God from another world meets a neuropsychiatrist and they fall in love", and it would have been a far more interesting story.

I know writing a review for this show means nothing now, because there will be plenty for everyone to read, and this will just get buried. But in the off-chance someone reads this: don't watch this drama. I'm annoyed I sat through all of it in the hopes that the water-deity plot would actually go somewhere at some point... spoiler: it didn't.

The 'water diety' plot doesn't go anywhere.
The powers he supposedly has? Don't mean a thing.
The characters (played by actors I like) are one dimensional and completely unrelatable.
The FL's tragic money struggles? Only turn up a few times, and don't change a thing.
Want to watch it for the romance? Sorry, it was unbelievable and boring.

PS: I apologise to anyone who actually enjoyed this drama, I just feel that everything this drama did was lazy, and I really hate it when dramas are lazy.