As I sit here looking out on the bay this summer and listen to my kids beg for a swimming raft....I wonder why I have not run across a plan for this before?  It seams to me a fairly straight forward raft, top side made with two or three sheets of plywood encased in 6 or 8 oz glass with two intergral sponsons under the rails wood make a somewhat light, very rigid and bouyant swim raft that would be cheaper in cost then the best aluminum sponson rafts ($2-2.5K) and be much sturdier and lighter than the lashed float/barrel and wood decking styles most people build.  I for one wood (pardon the pun) order the plans, epoxy & glass, wire and materials to build...maybe even spring for marine grade plywood.