It's a winning combination, and one that dogs appreciate as much as we do - possibly more.

But salt water can be hazardous, as Ned found out.

Ned, a solidly-built, 34 kilogram mixed breed rescue dog, loves a day at the beach according to his doting owners.

His favourite activities are wading and playing fetch in the waves.

Ned's owners ensure that he is fully supervised when in the water, so they could not understand when, after a long day at the beach involving an extended game of Frisbee, Ned became suddenly unwell.

He vomited a couple of times, and seemed unusually tired and flat. Even more concerning, his owners reported that Ned was walking with a bit of a wobble.

When I examined Ned, he seemed flatter than usual.

He was drooling excessively, licking his lips continuously and couldn't seem to settle.

According to his owners, Ned's tick prevention was up to date and he hadn't eaten anything toxic.

He did, however, swallow quite of a bit of sea water in the process of Frisbee-catching, and at one point when he got hot, had an extended drink from the water in which he was standing.

In the absence of alternative explanations, I suspected salt toxicity. Sea water contains a relatively high concentration of sodium chloride (around 3.5 per cent).

Blood tests revealed increased levels of sodium chloride, consistent with salt toxicity.

This is a condition occasionally seen in dogs after they consume large amounts of sea water, particularly when they have not had adequate drinking water.

It had been a hot summer day, and Ned had been particularly active.

Because he had been seen drinking, his owners hadn't thought to provide Ned with his own supply of drinking water.

These factors combined to cause some level of dehydration, which made Ned more prone to salt toxicity.

Signs include reduced appetite, excessive salivation, vomiting, diarrhoea, increased thirst, increased urination, muscle tremors or twitches, an uncoordinated gait, and in severe cases, seizures and loss of consciousness. In some cases, salt toxicity can be fatal.

Treatment requires slow correction of sodium levels, by administering intravenous fluids slowly, over a period of time.

This is because a rapid change in sodium can cause swelling of the brain (cerebral oedema).

I placed Ned on a drip and kept him in hospital the next day, until his clinical signs had resolved and his sodium level was normalised.

Salt water isn't a good way to quench thirst. It is vitally important that dogs are provided with fresh drinking water at regular intervals, with increased frequency on hot days - even if they're at the beach.

Dogs like Ned aren't always good at calling time on exercise.

If they're having a good time, as Ned was, dogs can exercise themselves to the point of harm.

Which is why we need to keep an eye out and encourage them to take regular breaks in the shade, with access to clean, cool drinking water. Portable drinking bowls with bottles are widely available so you can always ensure a supply.

Fortunately, Ned's owners acted as soon as they saw he was unwell.

He made a complete recovery, with no long-term effects. Importantly, he still gets to enjoy the beach.

Dr Anne Quain BVSc (Hons), MANZCVS (Animal Welfare), Dip ECAWBM (AWSEL) is a lecturer at the Sydney School of Veterinary Science and a practising veterinarian.