Dont worry. Its not blood. Its not even poisonous, just an irritant to skin and eyes and to anyone hoping for a swim now that summers finally about to hit Sydney.

A red algae bloom has closed 10 beaches so far in and around Sydney and up the more northerly Central Coast in Australia during the past 24 hours. And more beach closures could be on the way, say officials. But aside from some startlingly other-world pictures, it's not likely to scare away the tourists.

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The "crimson tide," or an algal bloom that has variously been compared to shark attacks or oily tomato sauce in the Aussie media, washed up on Sydney shores earlier this week, temporarily closing famed tourist beaches like Bondi. But it doesn't seem like too many around here are worried.

Turns out the blood-colored algal bloom isnt a result of pollution, but rather an upswelling of nutrient-rich waters that the buoyant algae can feed off. Two different blooms have apparently come from the same source and essentially floated to Sydneys shores. Their ammonia-rich diet can cause skin and eye irritations but little else problematic, according to experts.

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"This bloom has likely occurred as a result of the upwelling of nutrient-rich deep ocean water on to the continental shelf," the Metropolitan Sydney, South Coast, and Hunter Regional Algal Coordinating Committees told media Tuesday. They said tests had identified the algae as noctiluca scintillans or "Sea Sparkle" (for its phosphorescence) and pointed out that most algal blooms last around a week.

Despite the closure of Sydneys favorite beaches on the cusp of a hot summer and a possible heat wave of a weekend, with temperatures predicted to pass 100 Fahrenheit its doubtful this red tide will cause any longstanding problems either for locals or the tourism industry. And in the meantime, not all of Sydney's beaches are closed, and there are plenty of hotels with swimming pools.

And anyway, Australia has faced much worse in the water: Real blood in the water with the odd shark attacks, or stings from one of the many species of box jellyfish like the Chironex fleckeri, the worlds most venomous animal. The sting from this particular jellyfish can cause death in minutes, according to Australian jellyfish experts.

It will take much more to keep people from hitting Sydney's beaches.

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Red algae bloom closes Sydney's beaches, but probably not for long