Right so this is interesting. What size are we talking roughly? Like dog-sized or bigger? And what was the movement like - was it slow and steady or more sudden?
Asking because there's been a few reports over the years of large mustelids turning up in places they shouldn't be. Otters can get surprisingly big and look absolutely massive in low light near water, but if you're confident it wasn't that then something else is going on.
Also worth noting - were there any sounds? A lot of big cryptid-adjacent sightings near water come with either complete silence or a really specific low sound that people struggle to describe properly.
Post back with more detail, genuinely curious about this one.