A thoroughly average metroidvania.

+ the underwater setting is something I've not seen done before. As someone with thalassophobia, I found exploring both fascinating and dreadful
+ most of the boss battles were suitably epic

- the map was nearly useless and made backtracking a pain
- combat was clunky and made battles artificially difficult
- the ending was just not good

If you want to fight giant sea monsters, I'd say give this a go. Wait for a sale first.