Probably a decoy like this
Consider purchasing a frog log or critter skimmer, as both are relatively inexpensive and will help keep wildlife from drowning in your yard
Please do not give him water. You need to get Kaytee and feed this baby with a syringe, fill the crop every 4 hours. Retired rehabber here.
https://www.amazon.com/Kaytee-Exact-Hand-Feeding-Birds/dp/B0002DGJH8
It's a rat, but on behalf of my five rat daughters, please use a humane trap!! Harris Humane Mouse Trap, Catch and Release https://www.amazon.com/dp/B06XGG8LZ5/ref=cm_sw_r_cp_api_i_K7TTQX25S2NTD31CD7Y7?_encoding=UTF8&psc=1 I have this one, I had a mouse get it in the house, put some peanut butter in the trap and caught the little guy in a matter of hours. Just drop him off about a mile or two away from your property, and he won't come back.