Kaiser Seahorse would not work with Big Wave Small Wave, so that would only slow down your deck. Also, the suijin build might now mesh with what your deck's goal is - board wiping. Maybe add another twin swords and take out your sea amulet?
I have a similar deck and I feel this deck may slow you down when you don't have a good starting hand. The combo needs 4 cards(including umi) to initiate and your lower level monsters don't stay around that well(Yomi is gone when attacked and Moray's effect reduces your monster count). I suggest adding Angler and Suijin to reduce opportunity cost since the combo is easily countered by Kuribo.