到一定限度，超出该游泳运动员将失去他们的视觉感，较深的池允许波消散下到谷底，导致水少干扰泳客。
Up to a certain limit, beyond which swimmers will lose their sense of vision, deeper pools allow the waves to dissipate down to the bottom, leading to less water disturbance to the swimmers.
天龙座三剑客虽然并不像其他紧密星系群那麽出名，不过它们在视觉上的强烈对比，让它们成为天文摄影爱好者常常拍摄的对象之一。
Not as well known as other tight groupings of galaxies, the contrast in visual appearance makes this triplet an attractive subject for astrophotographers.
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