The invention relates to a boat (1) with a general contour defined by a periphery of predetermined shape and comprising a float (2) closed on itself along the periphery and formed by at least one floating tube (3); this tube is longer than this periphery and extends locally within the periphery towards the inside (INT) of the boat and has a curved portion (5) with a concavity turned towards the outside (EXT) and defining a re-entrant zone (7); a tent fabric (15) is fixed, along the periphery defining the general contour of the boat, to the tube except for the portion (5) defining the re-entrant zone (7).