A river is not a pond. It moves, it hides its floor, and its exits are whatever the bank happens to offer. The checks below take a few minutes standing on the bank with your dog on the lead, and they are the difference between choosing a swim and allowing one.
Judge the current at the bank
Watch the surface first. Floating leaves or a tossed stick show the speed: if debris travels faster than you could walk alongside it, the current is too strong for a swimming dog, whose paddling power is easy to overestimate from the bank. Look for the glassy tongues that mark deeper, faster water, for eddies that spin debris in circles, and for any weir, sluice or step downstream — a dog carried into any of those is in trouble you cannot wade into safely. Choose a stretch where the flow is slack near the edges and the dog can swim parallel to the bank rather than being pushed along it, and keep the session on the side of the river you are standing on, never a swim across to a bank whose exit you have not inspected.
Entry, exit and what lies under the surface
Walk the entry and exit points before the dog touches water. The dog needs a shelving, grippy way in and, more importantly, at least two places it can climb out unaided — a sloping gravel edge, a shallow shelf, a low grassy lip. Steep, muddy or undercut banks that a wet, tired dog cannot scramble up turn a swim into a rescue, and a dog who learns it cannot get out will panic in water it was enjoying a minute earlier. Test the exit yourself with a hand and a boot: if you cannot haul out, neither can the dog.
Then consider the unseen. Submerged branches and trees trap legs and collars; sudden drop-offs turn wading depth into swimming depth in one step; discarded line, wire and debris collect where currents slow. In clear shallow water you can see much of this; in murky water you cannot, which is itself a decision — unknown floor plus unknown depth argues for a different spot. Let the dog enter gradually where it can wade first, and keep swims short so tiredness never arrives mid-river.
Water quality, wildlife and the rinse afterwards
Look at the water's surface and margins. The algae rule is binding and allows no per-spot judgement: green scum or paint-like streaks on the water mean no swimming at all, anywhere in that stretch, however keen the dog is. Discoloured, foamy or chemical-smelling water gets the same answer. Calmer cautions still apply on clear water: avoid stretches below storm drains or where the water smells stagnant, and skip swimming if your dog has open cuts or has recently been unwell, raising it with your vet instead if you are unsure.
Share the bank politely. Livestock in the field means leads on and swimming reconsidered, since a dog chasing stock is a legal and welfare problem, not a recall challenge. Waterfowl with young, nesting banks and anglers' lines all argue for another stretch or another day. Only take the lead off at a stretch where the recall is already proven: a dog that returns reliably in the park must also return when wet, excited and mid-chase after a moorhen, and if that is uncertain, a long line keeps the swim and the control.
Rinse the dog with clean water afterwards, paying attention to ears, coat and paws, and dry it; river water left in a coat carries grit and whatever the river carried. Watch over the following hours for coughing, tiredness, vomiting or anything out of character after swallowing a lot of water, and contact your vet the same day if anything worries you.
The bankside checks cover the swim itself; the remaining risk is a dog carried or scrambling out beyond your sight and bolting along an unfamiliar bank. In KinsLe, Lost Pet Alert System coverage turns nearby dog owners into extra watchers, and the person who spots your dog can send you a message directly.