A tree-covered mass about 70 m by 140 m briefly floated on B.C.'s Williston Reservoir in late July and was confirmed by satellite on July 21. The roughly 9,800 sq m formation drew local attention after photos shared on Facebook. By August 5 it was no longer visible in satellite images; officials think it drifted into a cove rather than sank. B.C. Hydro says high water likely freed accumulated driftwood and vegetation, and boaters are warned about submerged hazards.
Mysterious Tree-Covered 'Island' Floats on B.C. Reservoir — Then Disappears
(Image via CBC News)
A large, tree-covered mass briefly floated on British Columbia's Williston Reservoir in late July before vanishing weeks later, baffling locals and officials.
The vegetation-covered formation was first reported in late July on the Williston Reservoir in northern B.C. — the province's largest reservoir. Roughly 70 metres wide and 140 metres long, it covered about 9,800 square metres, roughly the size of two NFL football fields.
Confirmed By Satellite
A local boater photographed the unusual sight and shared the images with resident Rocky Avery, whose Facebook post drew more than 140,000 views. Satellite imagery from July 21 confirmed the object afloat west of Finlay Bay, about 100 kilometres from the W.A.C. Bennett Dam.
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"It was a pretty amazing sight to see, never seen anything like that in my 40 years in this country," Avery told CBC News.
Officials Investigate, Then Lose Track
B.C. Hydro officials were initially skeptical of the photos because of the prevalence of AI-generated images online and because only a few first-hand reports were available. By August 5, updated satellite snapshots no longer showed the formation.
"We've been taking more updated snapshots and we can't see the object anymore. So it's disappeared now," said B.C. Hydro spokesperson Bob Gammer.
Officials suspect the mass did not sink but instead drifted into a sheltered cove or shallow inlet and moved out of view.
How Could a Floating Island Form?
B.C. Hydro offered a plausible explanation: an unusually heavy winter snowpack and steady summer rainfall pushed the Williston Reservoir to its highest level in 14 years. Over time, driftwood and organic debris can accumulate along shorelines, trapping soil, seeds and plants. When water levels surged, those mats of decomposing material, trees and vegetation can break loose and float as a cohesive mass.
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"We haven't had a full reservoir in 14 years," Gammer said. "We can't pinpoint the origin of this floating island [but that's] one explanation that seems reasonable."
Boater Warning
Although the floating island itself remains missing, locals warn that floating and submerged trees created by high water present a serious hazard to recreational boaters. Rocky Avery cautioned, "It'll do a lot of damage to your boat. So you got to be super careful."
Key facts: the object measured roughly 70 x 140 metres, was confirmed by satellite imagery on July 21, and disappeared from visible satellite imagery by August 5. Authorities believe high reservoir levels freed a driftwood-and-vegetation mat that later drifted away.
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