I use a indoor/outdoor wired probe that I picked up at Lowes for less than $10. I attached a large split shot to the end. Drop it in the water, wait until the temp readout stabilizes, remove from the water. Still working 2 years later. That will read to 10' depth.

Maybe the water resistant part is enough for short duration soakings?

www.hoosierpondpros.com

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3/4 to 1 1/4 ac pond LMB, SMB, PS, BG, RES, CC, YP, Bardello BG, (RBT & Blue Tilapia - seasonal).