This deck is kind of fishy. The opponent could be salty if they lose. Do you sea what I did there?

Great puns all!

I'd be interested in seeing the pros/cons of this vs mono blue. Not sure if you can play those Mutavaults reliably. Is Collected Company better than Master of the Waves? Against Fatal Push and Path to Exile it probably is.

I also think the sideboard could use some exploring. Kitchen Finks might be good against burn, which this deck is probably worse at beating in general. Is there some sweet UG card draw spell that doesn't cost 5+? Could be good as well against midrange.

hubatish, thank you for the feedback!

The reason I'm behind Simic instead of mono-blue is Merfolk Branchwalker is great and I have faith that Rivals of Ixalan will bring at least a couple more solid green or blue/green merfolk and I want to have a loose shell (weak pun, I know) drafted up for January. Depending on how that list performs, I may or may not be building this deck.

Now to address some of the other things you brought up:

• I haven't had any problems with the Mutavaults. Four were too many, but three feels just right.

• Lightning Bolt is at an all-time low. Fatal Push and Path to Exile are currently Modern's most common removal spells. That, coupled with the fact that the Devotion being split between two colors, is why Master of Waves didn't make the cut. Meanwhile, pairing Aether Vial with Collected Company lets me flood the board with my fishmen (and women).

• I haven't done much playtesting yet, but I agree that burn will probably be a problem. However, I haven't decided what to do about it. I could throw Kitchen Finks in the sideboard, I could run Wanderwine Hub and go Bant Fish for leyline and/or Kor Firewalker, I could play Dragon's Claw, or I could just suck it up and muddle through the burn matches. I have so many options, but I think I'm going to wait until RIX before I try to find my solution.

Maybe add Shaper's Sanctuary to the side