Could have seen that coming, to be honest it's surprising that they didn't employ weather magic at sea earlier. evictedSaint, Moskerg has gained in the western sea but that's still listed as Disputed, is there a territory counter hidden? Also what bonuses will they get if they manage to control the western sea?
Since the Jungle seems to be stabilised for now, and Myark will return there next turn, I think we should push them back at sea first. Improving on ebbor's design:
Crystal Galley: A ship designed for combat, with little space for landing troops. Following the dishonourable Muskerg deployment of weatherwizards on the waves, the finest minds of Arstotzka have turned their crystal conjuration skills to the naval theatre. The Crystal Galley has a layer of crystal covering its entire outer hull, strengthening it in ramming combat and incidentally making it faster, as it is no longer subject to fouling. A battering ram, made of the now-plentiful steel from the Arstotzkan mountains is affixed upon its bow, and the captains are taught to use ramming tactics against enemy vessels. Our wizards will first focus every effort into making the conjured crystal truly permanent, thus not needing a wizard onboard to maintain the conjuration, before worrying about the thickness of the crystal armour.
(Just to be clear, I'm proposing crystal armor only, not an entire ship conjured out of crystal. Interior hull and rooms will still be wood, or whatever we were previously making them out of.)
Oh, I'm also not voting for my own design, so +1 to Crystal Long Axe.