The three — Hayden Kyle, 21, Skye Donnet, 18, and Jule Wiltshire-Padfield, 15 — were paddling back to Rosebery from New Denver with 19-year-old Lily Harmer-Taylor when the group ran into trouble late Saturday afternoon.
Harmer-Taylor was found by rescuers in the partially-submerged canoe, but she could not be revived.
After boat and air searches of the lake and shoreline turned up no signs of the three missing friends, a 10-person RCMP dive team began an underwater search, focusing in the area of Bigelow Bay.
Police dive coordinator Doug Gambicourt says there are all kinds of challenges with the cold glacier-fed lake — but sheer depth is the main one.
"The guys were saying about 100 feet off shore, it just drops off into the abyss. And, of course, the canoe was out
beyond that," he said.
On Wednesday, Sgt. Darryl Little told CBC News that the RCMP dive team is limited in how deep it can go, typically 120 feet, or roughly 35 metres.
"What happens is we put two divers down on a sled that gets towed behind the boat, at various depths, so they can see the bottom, and [they are] searching for anything they can see down there."
"Where the canoe was found, there's a good chance that area is 480 feet (145 metres) deep. We wouldn't be able to dive that deep."
Police also tried out some sonar equipment earlier in the week, and on Thursday were expected to receive gear from Emergency B.C. that may help them see down as far as 400 feet (122 metres).
This weekend, a search crew from Vernon with better sonar equipment went out on the lake.
Gambicourt said it is frustrating for his divers to walk away from a site without recovering bodies.
"Last thing our guys want to do is walk away from a dive site, especially when there's young people involved. Without recoveries it's tough," he said.
Little said the families of the missing young men are being updated with the latest search efforts and their options going forward.
Those options may include hiring commercial dive operations with deep-water equipment to continue the search, or turning to a couple from Idaho, who located the bodies of two B.C. teens who drowned in Nicola Lake last year using their own underwater search robot.