Building an underwater home got you feeling blue? Well that's probably just asphyxiation! Why not craft yourself an helmet with the wonderful life-giving properties of oxygen to make those underwater jaunts more fun filled and less likely to end up with you floating belly up! Just charge these little beauties up and away you go, no more worrying about hard to find enchantments and remembering to keep an eye on those little bubble icons of doom.
"Power" could be from electricity, Canned air, or compressed empty cells or some other source. An much cheaper alternative to the quite epic QuantumSuit helmet. Would probably consist of basic circuits, an battery or cell or such, some refined iron, and either glass block or an iron helmet.