Totnes Raft race- Buoyant things required

In a moment of weakness I have agreed to do the Totnes Raft Race with work this year

www.totnesraftrace.co.uk/

We need to build our own raft for it, does anyone have anything buoyant they could donate/need to clear out of their garage etc? Old surfboards, buoys, canoes etc????

Thanks,

Carly