Your answer is correct. If you don't put the hose into the water, the water will fall when it leaves the hose, which means that you are throwing away potential energy. If you put the hose in the water you can make use of the siphon effect to let it flow by itself from a bucket.

Would a siphon work without atmosphere?

If there were no air pressure, could a siphon work? Yes, at least for some liquids, but something else would be required to cause the liquid to form a continuous path through the elevated U-tube.

Can you siphon water up?

A siphon is a way to carry water uphill without the use of pumps. ... A combination of gravity and atmospheric pressure drives the water through the hose, even if parts of the hose take the water uphill. Fill one container with water and place it on the higher surface.