sentence: Two divers are underwater in a controlled environment. sentence:  They are instructing on proper methods of using their equipment. sentence:  The diver on the left gives their mask to the diver on the right and he takes two deep breaths and returns the mask to the diver on the right. sentence:  She also takes two breaths and gives the mask back over to the diver on the right. sentence:  They do this roughly two more times between them and  they start to swim off which continuing to share the breathing mask until the camera fades to black.