I have a pair of Teva X-1 I am planning to take to Zion. I have forded a couple of local rivers in them. They dry slower than classic water shoes, but are much more sturdy and suitable for hiking. The mesh is very fine. I think grit is more likely to enter through the tops/sides of the shoe than the mesh. I am planning to couple these with waterproof socks in the river.
FOLLOW-UP: The Teva X-1 performed well on Canyoneer trips (Zion Narrows, Zion Subway). They shed water very well but took overnight to fully lose the damp feeling. Very versatile and did well on land, going 2000 ft down to the Subway or 1500 ft up Angels Landing.
The water socks (Sealskins water blocker) did not fare so well. They allow water in through the top if totally submerged. If you do not go below ankle deep in the water they are fine. They are somewhat fragile too, but the manufacturer, Danalco, was cool about replacing my pair gratis. In the future, if I am going to be submerged I would suggest quick-drying thin synthetic socks or neoprene socks if the water is very cold.