The back beach sits between the main part of Tahuna Beach we've shown you many times, and the Tahunanui Beach Motor Camp (arguably the largest camp ground in the Southern Hemisphere). Here's a satellite pic from Google Map.
The reason I wanted to show you this is that up until the 1960's (?), there used to be an annual car race held here on the back beach, but I can't find any documentation to go with the post. The Nelson Provincial Museum site has one pic by Geoffrey C Wood halfway down this page.
Nowawdays, of course, with bird habitats and whatnot, nobody would dream of resurrecting a race here... Different times.