Because the duck walked in the water, feet can be reduced buoyancy, can float on the surface of the water, and won't sink.

因为鸭子在水中行走的时候，脚可以减少浮力，能浮在水面上走，而不会沉下去。

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When the float upward force and float suffered gravity, buoyancy and viscous forces of the force equal to three when the float is in equilibrium.

当浮子上升的力与浮子所受的重力、浮力及粘性力三者的合力相等时，浮子处于平衡状态。

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The rest of the vertical column is made from a material called syntactic foam - a solid made mostly of hollow "microballoons" - giving it enough buoyancy to float back up.

BBC: James Cameron back on surface after deepest ocean dive