I just found Fool's Demise.  Might be neat here.

Merfolk Wayfinder will help you dig for lands and it flies.  Merrow Commerce counts as a merfolk spell and lets you not worry about blocking or tapping stuff.  Sejiri Merfolk is awesome with plains out.  Stonybrook Schoolmaster would be awesome if you could find a way to tap it, combo'd with Merrow Commerce, and just keep making merfolk at the end of each turn.

Hey broski, good news! Scared me on that first thought of "just tapping" lands. I guess the deal is, unless your land has an active ability, then yes or you cast an instant, then yes, because mana empties at the end of the turn, so I'd still get to use it.   

H'okay.  In response to drain power someone'd just tap all of their lands, so you get no mana.  Aside from something to prevent some sort of combat trick I don't see the point.  Sleep or a simple Counterspell would serve better.  You have a lot of stuff that makes things islands, but a simple pyroclasm would wreck your board.  Your big dude isn't going to start swinging until turn 7 at the best scenario, which totally sucks.  I like distortion strike a lot more, anyways.  Cast it, hit with the dude, take another turn it gets cast again, hit with the dude, take another turn and do whatever.  Also, if you are looking to continue to win once the dude starts hitting, you'd at least need four other merfolk to sac in order to keep taking turns (for four extra turns, plus the first, is 20 damage).  Why not something with merfolk tokens or splash white for some stonybrook dudes?