A keel also provides weight low under the water to lower the boat's center of gravity below the waterline, which is needed so that the boat bobs back upright if knocked over by wind or waves.

龙骨同时也增加了船只的底部重量，从而将船只重心降到吃水线之下，而这对于船只在被风浪打翻时能够得以及时回正是十分必要的。

youdao

The Arabic numerals are made of the steel plate; these numbers shall be set on the place from the suitable height above the keel to the height over the max. waterline drafts.

数字为阿拉伯数字，用钢板制成，设置在舭龙骨以上合适的高度起到营运吃水线的最大值高度。

youdao

The festival is like a swan -- all elegance and beauty above the water as the Angelinas, Gwyneths and Mischas reward the photographic phalanx with a dazzling dress and a sequined smile -- and beneath the waterline there is a flailing and scurrying of limbs as press and publicists beat each other over the head with whatever weapons they can muster.

CNN: Behind the red carpet at Cannes