What does Back somersault tucked mean?

Back somersault tucked meaning in Sports Dictionary

The diver gets a beneficial spring on takeoff, achieving up with his arms. The human body moves into an upward backward reach before you go into a tuck. The diver brings their legs up to his upper body and grips their shins. The elbows are tucked in to the edges before entering the water legs very first. (sport: scuba diving)