Replying to Twin tip water ski

so its now deep into the summer and i did not go to any ski camp and wished that i went to hood, which i didn't, but my family does have a boat that i like to ski, wakeboard and wakeskate on. my mind was drifting to skiing and thought that i could probably make twin tip water skis. i looked online, there are some made by hyperlite http://www.waterskis.com/2008-HO-WakeSkis-p/2008_ho_wakeskis%20(pair).htm but considering they're $400 i decided i'd make my own. i was thinking about making it like a marine-grade plywood, just it seems kinda heavy and i was wondering about any lighter material. i was wondering if anybody had any advice of what kind of material i should make it.