Lots of non replys here.

Its not that stupid an idea. Well maybe it is but Ive done it. Quite a few times in fact.
Back in the day when I was out chasing LW and was at the beach every day I went thru a stage of picking up every old body board I spotted from the kerbside waste & taking them down to Woodies to play with while waiting/hoping for some real wind.
Wasted many a precious moment - but hey - it was way more fun than sitting in the car cursing.
The small ones - forget it - that really is stupid. But the bigger ones - used as a skim in super shallows - Yep OK - but a tad flukey.
Go anywhere beyond a few inches deep & as soon as you get any power with the slightest off surface move - intentional or otherwise - results in 2 x half sized boards on the landing.
The 1/2 sized bits definitely didnt work