I had an old 20 gallon aquarium I was getting rid of that was still full of water. I brought a shop-vac over to the counter that the aquarium was sitting on but the hose was too short. I took the hose off and opened the lid to the shop-vac’s reservoir. I put the hose into the aquarium and figured I could start a siphon with my mouth and then aim the water into the bucket. I underestimated the speed of gravity. I just barely started the water moving through the hose when I felt like someone had punched me in the face. I was stunned for a moment as gallons of water enveloped my head and poured onto the floor before I regained my senses and steered what was left into the bucket.