Has anyone had a crack at mountainboarding downwind on the beach.

A cheap mountain board goes for around $300.00. They would have to have less resistance than a board on the water, therefor I should be able to get my speed up quite easily. With less wind in SE QLD for the next few months, I thought this could work.

I figure I could get motoring in around 10knts on the beach at Double Island. As long as I can dodge all the 4X4s, I could do a 30km downwind trek for sure. Any comments on past adventures?