A folding boat (11) with at least two foldable horizontal frames (12) each comprising at least two fold ably connected sections (12A), (12B) in one said frame (12) and (12C), (12D) in another said frame (12). Said sections are attached to each other by a transverse swivel joint (22) on one side and by releasable locking means (24) on another side. Said sections comprise two longitudinal rails (14) connected by a plurality of transverse members (16) and at least one swivelly foldable guard rail (26) with releasable locking means (32). Said longitudinal rails comprise internal (20) and external (18) longitudinal groves, where said internal longitudinal grooves hold a plurality of removable and stackable floats (46) with gasketted covers (48). Each said float comprises a substantially flat and vertical wall allowing said floats to be installed in pairs with mirror orientation to each other with their said flat and vertical walls contacting each other, so each pair of said floats forms a hydrodynamically shaped hull. Said foldable horizontal frames are connected by a plurality of removable horizontal transverse beams (34) secured to said transverse members by beams releasable locking means (38). Said horizontal transverse beams comprise longitudinal tabs (36) which together with said external longitudinal grooves of said longitudinal rails support and hold in place removable deck sheets (44).