FOLSOM (CBS13) – Plummeting water levels are fueling the search for answers in a decades old mystery at Folsom Lake.

Back in 1965, four people were killed when their plane went down in the lake — three of those bodies were never recovered. Now, the historically low lake levels are affecting renewed efforts to bring some closure.

READ MORE: Man Suspected Of 2017 Lodi Shooting Arrested In Tulare County

Among the sea of families peaking at Folsom’s Lake bed and its recently revealed history, there’s one with much more of a somber mission.

“When someone dies, it’s important for them to be laid to rest in a dignified manner — not be at the bottom of a lake,” said El Dorado County Sheriff’s Office Sgt. Dan Johnson.

A piece of the plane and one body was recovered at Folsom Lake about 50 years ago, but the search stopped before the other victims’ families could receive much-needed closure.

A couple from Idaho volunteered with their sonar boat, launching into the lake three days ago.

“They’re nationally known for their searching underwater,” said Johnson.

READ MORE: 17-Year-Old DUI Suspect Arrested After Deadly Crash In Tuolumne County

The couple has recovered dozens of bodies using their own $250,000 boat. It detects underwater objects and valleys, places plane parts could be.

Boaters say the low water levels on the lake make it difficult to launch; but on the other hand, the newly uncovered areas of the lake help narrow places to search.

There’s also the problem of silt — coating clues.

“There’s going to be more accumulation of silt as the water drops. It’s all going to drop down to the deepest points,” said Johnson.

After three days on the boat, they now have plenty of underwater images of area to investigate and for dive teams to go after.

Deputies believe that not just the bodies, but the plane’s wing and its fuselage, will all be uncovered with the eerily low waters revealing a nearly 50-year-old mystery.

MORE NEWS: Cal Fire: Fire That Started Under Foresthill Bridge Was Caused By Arson

Dive teams will head back into the water after a couple days of regrouping.