The "Water Candling" technique- people did that way back in the day. It is outdated (technically). Basically it is like a float test (for fresh eggs) and a flashlight. I have issues with it because of the gas exchange, etc- mother usually protects the young from such extreme changes in temperature, pressures, etc. I always go by 'if it is a baby on land- dont put it in the water'. I will echo you- I had some eggs where I said 'okay- they are no good, im going to throw in the towel'... woke up the next morning and I had chicks! lol.