Two men and two women were riding on three snowmobiles when they accidentally rode into the lake.
All four ended up in the water.
Three were able to get out of the frigid water, but a fourth was struggling.
A bystander brought a rope and helped pull the woman to safety.
All four were taken to the hospital.
Two had severe cases of Hypothermia.
The victims are identified as 22-year-old Megan Libby of Newcastle, her brother 19-year-old Earl Libby, 17-year-old Devon Jones of Nobleboro, and 21-year-old Jake Jewett of Errol, New Hampshire.