Is there such a thing. Or is there something anyone uses to check water temps from the bank. Would be cool to check water temps in the range and depths I can reach. 

Could always Just cast a pool thermometer

I figured that’s probably gonna be what happens. 

Way more expensive, but the Deeper Pro+ I have will give water temps as well.  If you're looking for a castable fish-finder, that's an option.

2 hours ago, CroakHunter said:

Could always Just cast a pool thermometer

It works.  I used a heavier rod with braid on it.

There are several stream thermometers available at reasonable prices that you could cast out. Google stream thermometers.