In BC lakes, the divers just fill little parachute-looking things with exhaust from their scuba gear. Presto! up they go.
BUT. . . . BC was not a part of the "Little Ice Age."
The hardwood logs in eastern North America, which lived through the LIA, cut, floated and sank back then. . . . that's the wood quality. Very simply presereved by inaccessibility. Too many people will try to tell you that it's the water-logging, the sinking that makes the wood so wonderful. Bunk. Hocus-pocus. Rubbish. Horse-puckey. Rot. No, it's because they couldn't chop it up back then. Really big, old barn timbers from the late 1700's are the same stuff.