How does external fertilization work in most fishes and amphibians?

In most fishes and amphibians, external fertilization is a reproductive strategy where eggs and sperm are released into the environment to unite outside the female's body.12

Fishes

Most bony fishes are oviparous, meaning they lay eggs that are fertilized externally. Females typically release a large number of eggs into the water, while males simultaneously release milt—a substance containing sperm—to fertilize them. Depending on the species, these eggs may be scattered in open water, attached to the substratum, or placed among plants. Because the eggs and developing embryos are exposed to the environment, they often face high mortality rates.13

Amphibians

While reproductive strategies among amphibians are diverse, many anurans (frogs and toads) utilize external fertilization. During mating, the male grasps the female in a copulatory embrace known as amplexus, which positions their cloacae in close proximity to ensure efficient fertilization. As the female deposits her eggs into the water, the male releases sperm over them. Some species have evolved specialized behaviors, such as building foam nests or using long cloacal tubes, to protect the eggs or improve fertilization success in challenging environments like flowing water.4567