Which of these is a fish?

Mudskippers are amphibious fish, presently included in the subfamily Oxudercinae, within the family Gobiidae (gobies). They typically live in intertidal habitats, and exhibit unique adaptations to this environment that are not found in most intertidal fishes, which typically survive the retreat of the tide by hiding under wet seaweed or in tide pools.

Compared with fully aquatic gobies, these fish present a range of peculiar behavioural and physiological adaptations to an amphibious lifestyle. Anatomical and behavioural adaptations that allow them to move effectively on land as well as in the water. As their name implies, these fish use their fins to move around in a series of skips.

Mudskippers are quite active when out of water, feeding and interacting with one another. They are found in tropical, subtropical, and temperate regions, including the Indo-Pacific and the Atlantic coast of Africa.