Bubble
From Worms Knowledge Base
(Up to Weapons (Worms Unlimited))
Bubble will protect a worm against 20% of the damage it receives. The bubble will disappear only when someone damage it, so it can exists for many turns. If a worm is already in a bubble and the weapon is used again, the protection will be 40%, if 3 times 60%, etc. It cannot be used more than 5 times (100% of the protection).