Apparatus including an inflatable enclosure delimited by a flexible wall to which an accessory is secured. The wall has an opening defined by an edge to which a protruding reinforcement is secured; two rigid frames straddle the edge of the opening on each side of the wall, at least one frame including a groove accommodating the reinforcement; the two frames are clamped against one another, trapping the reinforcement in the groove; the accessory is secured to a frame; and the accessory mounted on the wall is leaktight with respect to the fluid used for inflating the enclosure.