Can’t help you much. In Mexico, Used wading boots the first time I went, flip flops the second time. Then used flip flops and Simms flats sneaker for my last few trips in Maui.
On sand, some sort of sandal like teva’s Or whatever, might be good enough. Can’t see those orvis boots keeping all the sand out...and if you can’t keep it all out then what’s the point really?
That being said, they look like they’d keep more sand out than the flats boots.