1. The life jacket is made of a flotative material, ensuring the wearer's safety in water.
救生衣是由一种可以漂浮的材料制成的，确保穿戴者在水中的安全。

2. The density of the flotative device allows it to float effortlessly on the surface of the water.
这种浮力装置的密度使其能够毫不费力地漂浮在水面上。