An inflatable member projectile comprising: a projectile body having one end more buoyant than the other; an inflatable roll for vessel-immobilising; an inflation gas bottle at the less buoyant end of the body for inflating the inflatable roll and a cradle for supporting the roll in an orientation such that the inflatable roll unrolls in a generally pre-determined deployment direction, i.e. with the projectile floating with the less buoyant end down corresponding with their orientation. The cradle comprises a number of radiating channels, each locating one inflatable roll. Each roll has a serpentine portion in the bottom of its channel, for assisting in lifting the roll over a closed end of the channel. The cradle has a lifter for lifting the rolls up out of the cradle, actuated by the inflation gas.