Disclosed is a boat including a flexible bottom bordered radially towards the outside by a wall which includes an inflatable and flexible front wall, an inflatable and flexible lateral wall, and a rear wall. At least one part of at least one of the lateral wall and of the front wall is constituted by a first inflatable element configured as a panel having two parallel planar faces, a second inflatable element of which the cross section is in the form of a D with a planar portion, and a flexible assembly device, the second element being situated radially towards the outside of the boat with respect to the first element, the assembly device maintaining the planar portion of the second element in contact with one of the planar faces of the first element.

Disclosed is a boat including a flexible bottom bordered radially towards the outside by a wall which includes an inflatable and flexible front wall, an inflatable and flexible lateral wall, and a rear wall. At least one part of at least one of the lateral wall and of the front wall is constituted by a first inflatable element configured as a panel having two parallel planar faces, a second inflatable element of which the cross section is in the form of a D with a planar portion, and a flexible assembly device, the second element being situated radially towards the outside of the boat with respect to the first element, the assembly device maintaining the planar portion of the second element in contact with one of the planar faces of the first element.

A collar assembly for a watercraft includes an elongate tubular casing with a lengthwise sealable opening. A foam core is removably positioned in the tubular casing, and includes a body portion and a plurality of circumferentially spaced foam springs that extend outwardly to engage the tubular casing, to bias the foam core towards a center position in the tubular casing. In some embodiments a body portion of the foam core has a circular cross section, and the foam springs are co-formed with the body portion. In some embodiments the foam core comprises a plurality of longitudinal sections that are enclosed in a membrane having an inflation valve that extends through the tubular casing.

A collar assembly for a watercraft includes an elongate tubular casing with a lengthwise sealable opening. A foam core is removably positioned in the tubular casing, and includes a body portion and a plurality of circumferentially spaced foam springs that extend outwardly to engage the tubular casing, to bias the foam core towards a center position in the tubular casing. In some embodiments a body portion of the foam core has a circular cross section, and the foam springs are co-formed with the body portion. In some embodiments the foam core comprises a plurality of longitudinal sections that are enclosed in a membrane having an inflation valve that extends through the tubular casing.