I strongly suspect these are geoengineered "snowballs".

‘From another planet’: Waves of strange ‘snowballs’ found in Maine lake
RT News | Jan 6, 2016
http://on.rt.com/7144

[snip]

An artist visiting Maine to take photographs of his stone sculptures encountered waves of “snowballs” on Sebago Lake. Having posted the video of the undulating snow formation on Facebook, it went viral with 174,000 views.

Sculptor David Allen posted the video with the caption: “Waves of snowballs. This was one of the most awesome natural events I have ever seen!” on his Stone Point Studio Facebook page. The footage had nearly 3,000 shares by Tuesday afternoon.

“There was NO ice on the lake, so it isn’t lake ice. In fact it has been very warm, right up until we got this snow/sleet/freezing rain storm. It was very cold when I shot this, maybe around 20 degrees,” wrote Allen. He also shared videos and stills of a scene he described as “being from another planet.”

The “waves of snowballs” scene was posted to Allen’s page on December 29, and by Tuesday he had over 174,000 views. Though the balls look icy and hard in the video, Allen found they were actually the opposite.

“I fished out a couple of the balls, and sure enough, they broke apart and were very slushy, definitely not ice,” wrote Allen.