Try to keep your head and torso right at the surface, with very little up - and - down - motion.

尝试保持你的头和躯干正好在水面下, 只有很小的起伏波动.

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Using either a circular or jiggling up - and - down motion, brush this area with your toothbrush.

牙刷以圆周或者上下簸动的方式来刷这块区域.

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In addition to the up - and - down motion generated, surface waves also have a side - to - side motion.

除产生上下运动外, 面波还会发生侧向移动.

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