Necessary learning for sea diving: including how to use breathing tubes and regulators, resting methods on the surface, handling emergencies, etc. Preparation before entering the water is very important. Check whether the equipment is functioning properly by yourself, and check with each other among your teammates. Posture for entering the water: Diving upright from the front - the water depth must be more than 1.5 meters, stand your feet forward and backward, hold the mask with one hand, and press the air tube strap with the other hand. Entering the water while facing away - Sit on the boat facing inwards and enter the water with your back facing forward. Entering the water while sitting on the front - for beginners. Enter the water sideways - then float on the rubber boat and roll into the water. Descent: B.C. (buoyancy regulator) method - use a buoyancy regulator and a weight belt to descend head and feet. No B.C. - Head down and up. Ascent: Control the ascent speed within 18 meters per minute. Simply put, do not exceed the rising speed of the bubbles you exhale; do not stop breathing; when rising, look up at the water surface, you can extend your right hand to specify the direction, pay attention to your back, and slowly rotate your body .

The following patients are not suitable for diving: colds, neuropathy, ear and nose diseases, heart disease, high (low) blood pressure, drunkenness, diabetes, psychological factors, etc. In addition, people who have had thoracic surgery should not dive.

The difference between snorkeling and scuba diving: Scuba diving refers to a diving activity in which divers carry their own underwater breathing systems. For recreational scuba diving, divers use a complete set of scuba diving equipment including a buoyancy adjustment device (BCD), cylinder, regulator, diving suit, mask, diving boots, fins, pressure gauge set (residual pressure gauge, depth gauge , compass), a method of breathing for long periods of time by breathing compressed air in a cylinder. Snorkeling is a method of diving as long as the diver can hold his breath until he surfaces when he can no longer hold his breath.

Scuba diving rules: The maximum diving depth in the recreational diving field is 40 meters. The limit depth for junior open water divers OW is 18 meters. The theoretical maximum depth for advanced open water divers AOW is 30 meters. Divers must maintain their training experience when diving. Within limits, dive according to the diving leisure plan. When diving in unfamiliar waters, a local diving guide (diving guide) is also required. Principle of two people traveling together (buddy principle): two people must be together from entering the water to landing; the instructor is not allowed to allow the companion to land on his own; the two people must keep in touch frequently. What to do when you're alone: Stay calm, float a few meters up, and look for your companion; if you can't find one, surface and watch for bubbles. If there is still no sign of your companion after more than ten minutes, you should return to the place where you entered the water. Please do not hunt aquatic animals unless necessary. Check the remaining pressure gauge every ten meters. There are several common gestures in engineering: the situation is good---"OK", pay attention to the direction (of the object)--"the index finger indicates the direction", float up--"make a fist with the right hand, thumb up", dive---"make a fist with the right hand, Thumbs down”. Ear pressure equalization: For those who are diving for the first time or who have not been diving for a long time, the pressure of the water can cause discomfort or even pain in the ear canal. At this time, you should hold your nose with your hands and blow air into the nasal cavity with force, so as to increase the air pressure in the ear canal and offset the pressure of the water. If you dive further, the pain in the ear canal will be unbearable, so you should stop diving.