Sallyb

I have an above ground pool with a sand filter and heater. I went out to clean filters. Turned off pump and when I did the filter/skimmer basket on side of pool was blown with cover air and water into the air about 5 to 6 feet. Scared the crap out of me. Can you advise why this would happen, is it save to turn pump on again. I have left it off. Thank you.