Dogs and Water: A Love Story With Risks Worth Knowing
For many dogs, the sight of open water triggers irresistible excitement. Swimming is superb low-impact exercise — it builds muscle, protects joints, and burns energy efficiently. But each summer, veterinary practices deal with preventable tragedies linked to swimming: dogs that collapse after swallowing too much water, toxic algae exposure, and chronic ear infections that quietly reduce quality of life. None of these risks should stop a dog from swimming. All of them are manageable with the right knowledge.
Water Intoxication: Rarer Than Feared, But Real
Water intoxication, or hyponatraemia, occurs when a dog ingests so much water that sodium levels in the blood drop critically low. The result is cellular swelling, including in the brain, which can cause neurological symptoms, seizures, and in severe cases, death.
How It Happens
Dogs do not intend to drink while swimming — water enters the mouth during play, fetching, and diving. Dogs that obsessively retrieve from water, those that bite and snap at waves, and small dogs working hard to stay afloat are at greatest risk. The volume of water ingested over an extended session can be substantial.
Symptoms to Recognise
Early signs of water intoxication include lethargy, loss of coordination, vomiting, bloating, and glazed eyes. These can appear during or within a few hours of a swimming session. If you observe these signs after time in the water, treat this as a veterinary emergency. Time matters significantly with this condition.
Reducing the Risk
Limit sessions to twenty to thirty minutes at a time, with rest breaks on dry land. If your dog fixates on catching waves or biting water, interrupt this behaviour regularly. Dogs with a strong retrieve drive in water should be monitored particularly carefully.
Blue-Green Algae: The Risk That Looks Harmless
Blue-green algae are not true algae but cyanobacteria — microscopic organisms that bloom in warm, still, nutrient-rich freshwater during late summer. They can produce toxins that are acutely dangerous to dogs and can cause death within hours of exposure.
The appearance of a bloom varies. Some produce a blue-green or greenish-brown scum on the water's surface. Others look like pea soup or spilled paint. Some are not visible at all. A dog can be poisoned by swallowing water, licking its coat after swimming, or even through skin contact during prolonged exposure.
Symptoms of Algae Toxin Poisoning
Depending on the toxins present — hepatotoxins or neurotoxins — symptoms differ. Liver toxins cause vomiting, diarrhoea, jaundice, and abdominal pain developing over hours. Neurotoxins act faster: muscle tremors, seizures, respiratory failure, and collapse can occur within minutes to an hour of exposure. Either presentation requires immediate veterinary attention.
How to Protect Your Dog
- Check local authority or environment agency alerts for affected water bodies before visiting.
- Avoid any water with visible surface scum, unusual colour, or a musty or earthy smell.
- If in doubt, keep your dog out — no swim is worth the risk.
- If your dog swims in potentially affected water, rinse it thoroughly immediately and monitor closely.
- Do not let your dog drink from lakes, ponds, or slow-moving rivers during warm weather.
Swimmer's Ear and Chronic Ear Infections
Otitis externa — outer ear canal inflammation — is extremely common in dogs that swim regularly. Water trapped in the ear canal creates a warm, moist environment ideal for bacterial and yeast proliferation. Breeds with floppy ears, such as Cocker Spaniels and Basset Hounds, are particularly susceptible because reduced airflow slows drying. Dogs with narrow or hairy ear canals face similar challenges.
Signs of an Ear Problem
Head shaking, scratching at the ears, an unpleasant smell, discharge, redness visible at the ear opening, or sensitivity when the ear is touched all indicate a problem. Chronic infections, if untreated, can progress deeper into the ear and become significantly more complex to resolve.
Prevention and Management
After every swim, gently dry the outer ear with a soft cloth. Veterinary-approved ear-drying solutions can help remove residual moisture from the canal — ask your vet to recommend one suitable for your dog. Never insert cotton buds into the ear canal. If infections recur despite prevention measures, your vet may recommend investigating underlying allergies, which frequently manifest as ear disease in dogs.
Other Hazards Worth Considering
Strong currents, tidal conditions, and cold water are serious risks that less experienced dog owners sometimes underestimate. Dogs can tire or become hypothermic faster than expected, particularly in cold open water or after a prolonged session. Leptospirosis — a bacterial infection shed in the urine of infected wildlife — is present in many freshwater bodies across the UK and Europe. The leptospirosis vaccine does not cover all serovars, but vaccination significantly reduces risk. Discuss this with your vet if your dog swims regularly in natural water.
A well-fitted canine life jacket is appropriate for any dog in open water, particularly those new to swimming, elderly dogs, flat-faced breeds with compromised breathing, or dogs in areas with currents or boat traffic.
Making Swimming Safe and Enjoyable
- Check water safety alerts before every visit to natural water bodies.
- Limit sessions and include rest breaks to prevent water ingestion and fatigue.
- Rinse and dry your dog after every swim, paying attention to ears and coat folds.
- Ensure leptospirosis vaccination is current if swimming in freshwater.
- Supervise at all times — even confident swimmers can get into difficulty.
- At any sign of illness following swimming, contact your vet and mention the water source.
With appropriate precautions, swimming remains one of the finest forms of exercise available to dogs. The risks are real but manageable — being informed is the most effective safety measure of all.