And definitely put in a Sygg or two, it provides more ways to spend excess mana and also gives your mermen the benefit of protection whenever.

I'd replace the 4 Coralhelm Commanders with 4 Tidebinder Mages; since there's already 8 lords you don't really need 4 more slower ones and the Tidebinder really ramps up the control factor of the deck. Put in some Thassa's and you've got something to sink mana into. Throw in some Triton Tactics and you've got more ways to make up for the fact that you'll probably have open mana with so many 2 drops.