In scyphozoan jellyfish, the free-swimming medusa form is the dominant stage, with the sessile polyp form found only during larval development.

自泳的水母见于各海洋，包括常见的沿海岸线漂流的盘形动物(甲壳动物)。

In the adult, or medusa stage of a jellyfish, they can reproduce sexually by releasing sperm and eggs into the water, forming a planula.

在海蜇成体或水母体阶段，它们通过将精子和卵于水中形成浮浪幼体而进行有性繁殖。