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.