All the eggs I ever did this with except for 2 have all sunk. Both eggs you see sunk and when I candled them they were alive. The weight vs air cell is why they sink..not death. The ones in the incubator ALL sunk and all are alive ready to hatch. The Water test is the correct term and floating...
Day 21 both alive. I did break away outer shell from pointy end where 1 twin is..both still alive..one piped "internally" already but I broke shell away.