Diving into the water without an oxygen tank is called ‘free-diving.’ It is a form of apnea diving in which divers must hold their breath for an extended period while diving deep into the water with just one breath of oxygen. The difficulty in holding the diver’s breath during this time is not due to a lack of oxygen but rather an increase in carbon dioxide concentration. In other words, if you keep your heart rate low and your metabolism slow, you produce less carbon dioxide, which allows you to dive for a longer duration. The only way to maintain a low heart rate is to remain as calm as possible. Maintaining calmness has numerous benefits in life. - Joseph’s “just my thoughts”
A lifetime of tuna is about 10 years. They don't have any muscles to suck the water up and constantly have to be moving their bodies to breathe in the water. So, they can not be sleeping or resting a lifetime of tuna. Even going to sleep, tuna must keep on moving in a sleep-like state until their deaths, if they stop moving, they will be dead soon. According to the attribution, tuna can swim in water at over 100 km/h speed, they need so many other fishes as foods to supply the wasted energy for this fact. The tuna is paid for the huge price of becoming a top-rated predator. But I'm not a top predator, so why do I eat so much? - Joseph’s “just my thoughts”