Not exactly the same situation but we've got big cat sightings here in Scotland pretty regularly, the "Beast of Meigle" type stuff, and the pattern is always the same - same general area, near water, usually at dusk. So the creek detail really stands out to me.
What size are we talking? Like actual panther-sized or could it have been a very big domestic? And was the coat completely black or could it have been very dark brown in certain light? That detail matters a lot for ruling things out.
Genuinely would love to see your photos or sketches if you have any. Also worth checking if local farmers in the area have reported missing livestock, that tends to be the paper trail that confirms these things are real and not just one-off sightings.