Don't Laugh Portable Fish Finder

[Balvar24]

Does anyone have experience with these?  Specifically the castable ones that use your phone for a screen?

They looked like fun with the canoe and off the bank.

Lawrence and Vexilar both make one.

[festus]

I have a Hawkeye and another, maybe a Venterior.  Never used either one of them.  Unused Christmas gifts continue to pile up.

[Balvar24]

 $10?