this sounds like nineteenth century science fiction but one of the allies’ secret weapons in world war 2 was to be a ship made of pykrete. there’s nothing special about pykrete, in fact it’s just ice mixed with wood pulp, but amazingly it’s more than twice as strong as normal ice when a projectile (such as those pesky torpedos) was fired at it. the british planned to make huge ships from this material to serve as remote aircraft bases, but alas another secret weapon, the atom bomb proved more useful.