What water pokemon are you seeing?
I find Dratini along rivers/lakes where there are tons of Magikarp, Psyduck and Slowpokes (with occasional other water pokemon) but that doesn't mean it's exactly the same in your town.
I don't ever camp the water spawns, rather I have a morning run along the river so I can cover a good distance (5K) and I find about an average of 2 dratini a day doing this.
Lapras don't spawn in Austin, TX at all .. so can't help you find those.
Dragonites I have only heard about spawning in other areas .. mostly not next to water.