"Let me show you." Belle dives underwater, finds the waist line of his trunks and unties the strings. She smacks his butt so that he raises it out of surprise and takes that instant of lift to pull his trunks down. When she has them around his thighs she can see his hardening member. She takes it in her mouth, going as deep as she can and then removes her mouth and continues removing the trunk, coming up for air with them in her hands.