Hey guys, thanks for the comments, this is exactly what i went and did (1/8 square balsa to be exact on the sides and bottom).

Ive never done anything related to fiberglass which is a shock horror considering my old man works for boeing making components for the 787, and always brings home off cuts and stuff that didnt past testing, the stuff is bloody strong. it is definitely something i want to give a try (I am looking into making airboats) but really dont know where to start, what exact materials i need and at the moment money is a bit tight so cant afford to buy larger/in bulk orders

Damo