Dugongs may look like seals or dolphins, and are colloquially referred to as “sea cows” because of their diet of sea grass, but they are actually related to neither. In fact, sirenians (the mammalian order which includes dugongs) are a member of the clade Paenungulata, which also includes the elephants and hyraxes. This clade evolved from primitive hoofed mammals that lived on the shores of the Tethys Ocean. The families began to diverge sometime in the early Eocene, and the first sirenians were pig-like, four-legged mammals that lived both on the shore and in the water (seen in the lowest image).
Portuguese man of war look like jellyfish, but each “individual” is actually a colony of four different types of polyp. For example, one of the organisms is the float, or pneumatophore, which helps in passive locomotion. Another consists of the tentacles that trap food so that nourishment can be shared throughout the colony.