Bubble Shield is a WAAPT-exclusive move originally created by the Suicune of the Oblivia Legendary Beasts, which has since then been tutored to several other water type Pokémon, such as Lake and Iggy amongst others.
Bubble Shield is a move akin to a water type Substitute. However, rather than creating a plush likeness/a layer of armor to absorb hits, the user instead envelopes themselves in a bubble, in a similar fashion to how one would blow a Dive Bubble. However, like Substitute, blowing a Bubble Shield will cost the user 1/4 of their HP, which will create a Bubble large enough to protect the user. More HP, however, can be expended to make the bubble large enough to protect multiple peoplemons...or simply for showing off.
A typical Bubble Shield is a large semi-transparent bubble of a certain color that differs depending on the user, although they are most commonly a shade of blue. Although made of water, they have a consistency similar to a sort of soft rubber or plastic, meaning it will easily give if you press against it, but is still firm enough to not be punctured without applying a large amount of pressure.
As mentioned prior, a typical Bubble is large enough to cover the user completely while still giving them ample room to move without banging their head or limbs on the sides of it, however, they can be made larger (or smaller) on the user's whim, providing that they have a HP pool large enough to invest in creating one.
An occupant of a Bubble will still be able to breath and hear what's going on outside of it, despite the actual shield itself being air-tight. Unlike a Protect or a Safeguard, the bottom of a Bubble Shield does not "phase" through the surface it is stood upon. As such, it will roll like a ball when pushed, either from the inside by the user, or from an external force, which can prove rather problematic when fighting savvy opponents. It is not uncommon for an opponent to take advantage of a bubbled target by striking in just the right way to send them pin-balling around the battlefield.
Unlike a Dive Bubble, which can easily be burst if the user is not careful, a Bubble Shield can withstand far more serious blows without being punctured. However, unlike a Substitute, a Bubble Shield has the traits of a water type target, and will therefore take increased damage from Electric and Grass type moves, and decreased damage from Fire, Ice, Steel and Water moves. Upon taking too much damage, the bubble will pop; leaving whomever was inside it vulnerable (and most likely soaked with soapy water).
As well as providing protection against damaging attacks, a Bubble Shield will also shield the user from hazards such as sandstorms, hailstones, dangerously low or high temperatures, Toxic fumes, and lack of oxygen.
While primarily being used defensively, Bubble Shield has a more offensive use in being able to trap an opponent and hold it in place, hopefully long enough to be able use a powerful technique against them. Your foe will be most likely be far too preoccupied trying to burst their make-shift prison to see that Focus Blast or Thunder coming their way.
Bubbles created by this move have various other usages. One of the most common is to blow a bubble to sleep on or inside as a make-shift bed or tent. Another common use is as a form of trampoline, as they can be quite easily bounced upon to gain a large amount of air. Finally, a large amount of smaller bubbles can be stuck together to form large structures such as tents, houses, or even castles. Thanks to their durability, they can serve as a viable building material, as demonstrated by the Oblivia Beasts and their so called "Bubble Fort."
Oh, and a word of warning: Do not pop a Bubble Shield while Pankaja is around. He will make you pay.