Often called the clearest and least spoiled river in Texas, and it is clear for a specific reason: almost all of its water arrives as spring flow through limestone rather than as runoff, so it carries very little sediment. It runs through country with essentially no towns on it, and access is so limited that the state manages both a natural area and a paddling permit system for it. Below here the river disappears into Amistad Reservoir.
Getting there
29.9540, -101.0230
Locations are approximate and may be inaccurate, on private land, or otherwise inaccessible. Check before you travel.