I’m no expert but the tail is wrong for a Savanna and the spots are wrong for Bengal. The closest thing picture wise I found was a Leopard cat. If that’s the case it probably was dumped on the river when it got mean?
Bengals can be spotted (vs.rosettes) as well, but likely not as heavily spotted as the cat in the OP's pic.
Egyptian Mau is another candidate among others for a domesticated cat, but again not so heavily spotted.
I have no idea what the cat really is....except to say its probably a house-cat of some type and not a bobcat variant.