MArcomage

Interesting but Leviathan and Ocean queen together? Is it playable?
I'd prefer Poseidon's Wrath instead of Leviathan and Sea priestess instead of Mermaid.

It might be done, but then you only have one rare card, that's Ocean queen.
Also Sea priestess is super useless imho.

Ocean Queen can be a killer if played after Sea lord or Whale. At least in normal mode.

Water Dragon could also be used instead of Leviathan. I find Leviathan to be too expensive to fit in this... not that I wouldn't use this card as it is. :)