How to find the perfect ocean conditions year-round
Don’t like swimming in chilly seas? We tell you where to go here and overseas, with some surprising inclusions.
Numbers are everything in a day in the life of Guy Dunstan. The first number is 3.30. That’s the time his alarm goes off each morning, although the Manly resident – known to his 13,000 social media followers simply as “The Temperature Guy” – says he’s usually already wide awake, contemplating the mission ahead.
He leaves his house carrying a few essentials: a flood light, some coloured chalk, a bag of rags, a towel and – most important of all – a Weber barbecue meat thermometer. Come hell or high water, Dunstan walks to the southern end of Manly Beach, wades into the ocean and measures the water temperature. He then writes the numbers in large, artful lettering on a concrete drain near the surf club, along with a daily drawing, and uploads a short video for his followers. The highest reading Dunstan has recorded is 24.6C; the lowest just 14.2C. “Anything below 15 puts you into cold shock,” he says.
Water temperature is always a hot (or cold) topic of discussion for members of The Bold & the Beautiful, a recreational swimming group that meets at 7am daily to swim 1.5km from Manly to Shelly Beach and back. “A lot of people won’t go in unless they know the water temperature,” says group co-ordinator Ian Forster. “Some have a threshold temperature for when they’ll put their wetsuit on. And Guy has made an art form of conveying that information.”
You don’t have to be a regular swimmer to be attuned to water temperatures. It’s one of the first things we think about when planning any holiday involving water immersion.
Growing up in New Zealand, I thought I knew cold water. But the snow-fed rivers of the Southern Alps were nothing on Windermere, England’s largest lake, which despite it being summer left me gasping. The warmest waters I’ve swum in would have to be the bathtub-like beaches of Borneo.
Globally, water temperatures are rising at an alarming rate. UNESCO’s State of the Ocean Report indicates the ocean is warming at twice the rate it was 20 years ago, a consequence of the ocean absorbing 90 per cent of excess heat trapped in the atmosphere. And because water molecules expand as they heat up, this becomes a driver of rising sea levels. The increase has been noticeable even to the casual swimmer, according to Jack Hudson, from British-based swimming tour operator SwimTrek: “The rate of warming has doubled in the two decades since we were founded; it’s a continuous concern for us.”
Hudson says many swimmers will ask early in the booking process how cold the waters are likely to be, whereas others try to avoid warm water, which can present problems for long-distance swimmers. He says the warmest waters on their trips are found in The Maldives, the Bahamas and the Red Sea, while their coldest water destinations are the Isle of Skye and the Outer Hebrides in Scotland. “The recent trend of cold water therapy means more swimmers are now drawn to these colder trips, for the benefits gained from natural sea bathing in lower temperatures,” says Hudson. “Conditioning is a highly important and prolonged process that should be taken seriously, though. You can’t rush into waters much colder than you’re used to and expect to be unaffected.”
According to the Bureau of Meteorology, the average sea temperature around Australia has warmed by 1.08C since 1900, with nine of the 10 warmest years occurring since 2010. It comes as no surprise to learn that our warmest waters are in the tropical north, from the Pilbara across to the Gulf of Carpentaria and up to the Torres Strait. Here, the temperature can routinely reach 32C. At the other end of the spectrum, sea surface temperatures in Tasmania can get as low as 11C.
I can attest to the frigidity of Tasmanian waters, having been subjected to the near-death experience of a Wim Hof Method cold water therapy session in the sea off Swansea in October a few years ago. I mention the month because it highlights the interesting fact that ocean temperatures are slow to catch up with the changing seasons. The sea tends to be at its warmest in early autumn, and at its coldest heading into spring. Members of The Bold & The Beautiful know the water will probably be warmer at Easter than at Christmas, and that you’re more likely to reach for the wetsuit in September than June. It’s the same everywhere, so if you’re planning a shoulder-season European holiday but worried the water might bite, book for the end of summer, not the start.
Just as with air temperature, seasonal variations in water temperature are more pronounced the farther you go south, which is a big reason why 686,000 Victorians (myself being one of them) fled for holidays in Queensland between April and September last year. The ocean in summer though can feel positively balmy in Tasmania, especially on the east coast around the beautiful beaches of the Bay of Fires. Much of this is due to the East Australian Current, Australia’s largest and most influential coastal current, which pushes warm water from northern Queensland down the NSW east coast (you might recall it as the underwater superhighway that propelled Nemo and friends towards Sydney in Finding Nemo).
According to Taimoor Sohail, a research fellow at the School of Geography, Earth and Atmospheric Sciences at the University of Melbourne, the current is at its strongest in summer, and will often shed rotating eddies of warm water down the Tasmanian east coast. “During winter the current weakens and retreats north, limiting its influence on southern Australian ocean temperatures,” he says.
While a strong EAC flow might be nice for swimmers, a prolonged period of anomalously warm water – known as a marine heatwave – is bad news for marine species. Dr Jessica Benthuysen, an oceanographer at the Australian Institute of Marine Science, says the increasing influence of the nutrient-weak EAC is killing Tasmanian kelp forests. Benthuysen is working on understanding changes in ocean temperatures along the Great Barrier Reef, and what that means for coral health. “We’re seeing bleaching events occurring a lot, and this summer parts of the reef experienced heat stress events. Bleaching is starting to occur off Western Australia now, too.” She says the Great Barrier Reef often blocks warm currents from reaching the coast, an effect known as coastal cooling. It’s partly for this reason that coastal waters in Queensland are generally a few degrees cooler than waters of the same latitude in Western Australia.
Currents have a huge influence on WA’s water temperatures. The main northern current is the Indonesian Throughflow, which filters down through the Indonesian archipelago, warming the waters of the Kimberley, while the warm Leeuwin Current caresses the coast from the Pilbara south to Cape Leeuwin, wrapping around into the Great Australian Bight. What’s interesting is that the current keeps to the west of Rottnest Island. As a consequence, the beaches on that side of the island are usually several degrees warmer than beaches in Perth. Unlike the EAC, the Leeuwin Current is typically strongest in winter, which is one reason the water temperature in Margaret River doesn’t plummet in winter the way it does in Mallacoota, Victoria.
Fluctuations in ocean temperature are also caused by the wind. Northeasterlies along the east coast will push warm surface water away from the shore (it sounds counterintuitive, but trust me) with cooler, deeper waters rising up to fill the void. The effect is called upwelling, and it’s a common occurrence during summer in my home town of Kiama, on the NSW South Coast. “You’ll go for a swim one day and notice it’s a few degrees cooler than usual,” says Kiama resident and long-time water baby Michael Stoboi, otherwise known as my uncle Mike.
The phenomenon happens regularly in Sydney, too, providing endless fodder for chatter among The Bold & The Beautiful when they arrive at Manly Beach each morning to read the latest numbers. Guy Dunstan can’t quite believe the response to his daily doodles on a drain. “People are so passionate about … the water temperature, but I think it goes deeper than that. No matter where you are in the world, no matter what you’re going through, for a small moment in the day you’re transported to Manly. I’ve had people say these numbers have kept them alive. They’ve given people a lot of joy. It’s my gift to the community.”
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