So I've played the new Halloween Operation in Public Test many times already, even got 3 stars once and have twice hit over 400k damage. At the moment, I have the Barracuda and the Zipper Sub (I think that was originally going to be named Krokha). Most players I have come across on the test server only have one submarine, the Barracuda. I don't even know how I unlocked the Zipper Sub. Also, does anyone know how to unlock the other three submarines?