The briny blue has looked more like a certain pool in Rio lately, thanks to a massive algae bloom turning the ocean emerald.

The pool of bright green water off the coast of the Lower Mainland is so large it can be seen from space, visible from NASA satellites over the last two weeks.

In some places, the water is so vibrant that you don't need a satellite to spot the change in colour. But many are confused about what's causing the verdant pools to form between Vancouver Island and the mainland.

"It kind of just looks beautiful. I don't know if I think of it as a bad thing or a positive thing. It just looks nice," a visitor to Horseshoe Bay told CTV News.

"I'm going for a swim in it later. Hopefully it doesn't eat me alive."

Some who spot the stark change in water colour are worried the green patches may be toxic, like red tides.

Last year, a huge bloom of toxic algae temporarily shut down fisheries and tainted seafood. The bloom that stretched along the west coast was dominated by a type of algae that produces a neurotoxin called domoic acid. The acid can be harmful to people, fish and marine life including seals and birds.

But experts say the bright green algae filling Howe Sound and other areas along the coast is not dangerous.

Nicky Haigh of the Vancouver Island University's Harmful Algae Monitoring Program said the colour is caused by tiny phytoplankton called coccolithophorids.

"They're about a hundredth of a millimetre across," Haigh said of the tiny aquatic algae.

The species of phytoplankton has tiny scales on them that reflect the light, making the water look "chalky," she said.

"This is an unusual bloom to be seeing in the Strait of Georgia. We usually see different species… We're not really sure why they're blooming in this area."

Coccolithophorids are common off the west coast of Vancouver Island in June and July, but are rarely seen between the island and the mainland.

Some have suggested the temperature this summer has brought the species to the strait, but Haigh said the temperature hasn't varied much from previous years.

"We think perhaps it's an ocean acidification thing, which is obviously linked to climate change," she said.

Her team has seen waters with a higher acidity in the strait in the last five years, and they know from previous research that waters with a lower pH can encourage growth of coccolithophorids.

The bloom could also be due to a change in nutrients, or competition with other algae.

"We see a lot of different species of phytoplankton and sometimes some of them do better than others, and it's kind of hard to pinpoint what the factors are of that," Haigh said.

With a report from CTV Vancouver's Nafeesa Karim