7 seems a bit much for freezing 1 creature per turn. Arctic Squid CONGEALS 1 creature per turn for 1
Actually its 2
also....
1. Arctic squid is a creature and so is targetable by CC and also has very low HP so that it doesnt last long.
2. Arctic squid cant use its ability the first turn
3. Arctic squid has to keep casting it every turn (after 3 turns or so it ends up costing more)
That being said, arctic squid gets you to target which you hit. Also by making the cost so high it would likely limit its use to mono water or at best dual decks which is a shame. Perhaps 6, but you can't go much lower without it becoming OP.
This could be very powerful if combined with arctic squids, so if an attack slips through it too is frozen. But I question is water needs yet another way to freeze - it has freeze/icebolt/iceshield/arctic squid already. But could make an interesting addition - after all its not above PC