Hi Vasteq,
cool, I mean once I've seen the same or a similar fern. Let's see if it will thrive submersed. IMO it belongs to the family Hymenophyllaceae indeed, but I don't know which genus. Anyway, seemingly there is no consensus among the botanists regarding classification of the many species (Crepidomanes / Trichomanes / Vandenboschia?).
There are sori on the leaves:
Gruß
Heiko