1·In fact, tunas must swim to breathe.
事实上，金枪鱼必须游泳才能呼吸。
2·Tunas, mackerels, and billfishes have even more sophisticated adaptations than these to improve their hydrodynamics.
金枪鱼、鲭鱼和长嘴鱼有比这些更复杂的适应性，以提高自己的流体动力学。