That makes sense then as Bala Falls and the wrecks around Christian Island are quite warm in the summer and 3 mil would work. Don't try diving wrecks like the Arabia in Tobermory in a 3 mil or you will likely end up as a casualty.You're right - I should have specified. We've done most of ours in Georgian Bay, as my place is right on the southern edge. Dive sites include places near Christian Island, Giants Tomb Island and several smaller shore dive wrecks. We've also done a bit in the river below Bala falls.