Essentially you are building Modern Merfolk, it looks like :) It is an established deck, if you want a reference here is a list of the top merfolk decks.
@Dalektable I suppose there is always someone who has it. Its an original build, but certainly not an original idea.
@irjeff Phantasmal Image looks like it would be awesome here. Already using thassa, Aether Vial will be perfect, and Merrow Reejerey would replace Hall of Triumph? Do you think Merrow is better? Or do you think that keeping Master of Waves' tokens is equally as good?
Sorry, must have overlooked thassa. In my opinion, I think keeping the base of the deck as strong as it can be is the thing to do. With that in mind, Merrow Reejerey would be most optimal since it helps the base of the deck. There are more merfolk, than Master of Waves , so just statistically it seems better. Plus merrow gives some utility as well.
I agree Merrow Reejerey would be an excellent addition. He's cheap and adds consistency. Even if you just untap a land each time you cast a merfolk, he has effectively lowered your entire decks casting cost by 1. Each merfolk you cast could alternatively remove a blocker by tapping it prior to combat. He's full of trickery.Reef Shaman / Streambed Aquitects / Tidal Warrior / Tideshaper Mystic are nice if you want to take advantage of islandwalk.My personal favorite merfolk is Rootwater Thief . Nothing makes me giggle like removing key combo pieces from an opponents deck. Also, True-Name Nemesis is just wacky to play in single matches.
Rather than using Counterspell , why don't you consider Remand ? It helps you with your tempo, it can save your own stuff from counterspells, and best of all, it replaces itself. Plus Counterspell isn't modern legal.
@ Nomp really like merrow commerce, gonna find a place for it