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Is it Safe to Swim?

Is it Safe to Swim?

The summer swimming season is a great opportunity to enjoy our coast and waterways. They are usually safe to swim and play in, but there are some times and places where caution is needed.

Toxic Algae

When the weather is dry our rivers can produce toxic algal blooms, especially where the water is already shallow.

The algae grows on submerged riverstones in a shiny brown/dark green coating or as dark brown strands. When it dies it floats to the surface and forms small brown or white mats at the water’s edge. These mats are highly poisonous and can quickly kill if swallowed. It is important to keep an eye on babies and toddlers who are naturally inclined to put objects in their mouths. Seek emergency medical attention if anyone in your group accidentally swallows toxic algae in even small amounts (coin sized).

If you have been swimming in a river or lake and you feel unwell and have any of the following symptoms: nausea, vomiting, numbness, tingling, muscle twitches, shaking, weakness, breathing difficulties and potentially convulsions and loss of consciousness see your doctor immediately.

Dogs are at greatest risk from toxic algae because they love the smell of it and will eat it if they can. During a bloom, they must be kept on a leash along the river bank. If you suspect your dog has eaten even a small amount of toxic algae (coin sized) take it straight to the vet.

Greater Wellington is monitoring popular swimming spots weekly throughout the summer. We will issue an alert if toxic algae reaches unsafe levels, but please learn to recognise and avoid it.

Toxic algae in depth

Tummy Bugs

Stormwater entering our rivers brings with it a small amount of waste from animals (such as birds and dogs) and sometimes untreated human sewage from overflows. This can be a significant health risk after heavy rain. Only swim when the water is clear – this applies to rivers or the sea – and wait for 48 hours after heavy rain. Another good guide is “can I see my feet when I’m standing up to my knees in the water?”

Our water quality map shows the overall water quality at 85 sites around the region. It is updated weekly from 1 December – 31 March. If you notice a problem with water quality you can report it on 0800 496 734.

Learn more

National water quality information

If you are travelling outside of the Greater Wellington region you can find national water quality information on LAWA. LAWA is a key resource for measuring the current state of New Zealand's waterways and shows longer-term trends, information and data.

Toxic Algae levels are high in the Hutt River, upstream of Silverstream bridge. We advise against swimming in that section of the river, and that you keep your dog on a leash if walking nearby. Birchville, Maoribank Corner, and Poets Park also have new growth, though at lower levels.