The man who captured them on camera says they formed when ice coated rotten apples and the fruit itself slipped through as apples have a lower freezing point than water.
Normally, the temperature in northeast Greenland, in April, is around minus 20 degrees Celsius, but that week, we had days where the temperature was above the freezing point.
Even though the surface of the sea has solidified into ice, its lower strata are still open, thanks to that divine justice that puts the maximum density of salt water one degree above its freezing point.
The Celsius scale uses the freezing point of water as its zero degree mark, so in other words, when it starts to get cold enough that liquid water becomes solid ice, that's zero degrees Celsius.
You may walk into a room that is very cold and say, " It's freezing in here." You don't mean it's actually below 32 degrees Fahrenheit, which is the freezing point for water.