The hydra moves upside down by freeing the feet. That is, the foot is on the top and the oral floor is on the bottom. Gas and mucus are secreted from the glands of the soles of the feet. The released gas and mucus combine to form bubbles. Hydra floats in water with the help of bubbles. During this time, it floats from one place to another due to the pull of the current or the impact of the waves.