Misc: In 1939 The Soviet Union invades ---------- over a border dispute. ?

Questions

Water in vapor state, used in the generation of power & on a large scale in many industrial processes?

Water filled tank, usually with glass sides, in which aquatic plants & animals, particularly fish, are kept?

Waves break when their height is how much more than the depth of the water?

Weapon resembling a short sword or a dagger, designed to be attached to the muzzle of a rifle or musket?

Weight carrying structure that can travel through the air, supported either by its own buoyancy or by the dynamic action of the air against its surfaces?