While diving in tropical waters, you may come across what appears to be a bed of seagrass gently moving with the current. But look more closely—you may actually be swimming among a colony of spotted garden eels (Heteroconger hassi), slim and straw-like fish often mistaken for plants, which live the majority of their lives partially embedded in the sea floor. One of many species in the subfamily Heterocongrinae, spotted garden eels live in areas with strong currents, where they sway together in large groups, feeding on passing zooplankton; there can be hundreds to thousands of eels in a single colony. Garden eels may be small compared to other eel species (only half an inch in diameter), but what they lack in size, they make up for in muscle. H. hassi uses its stiff, muscular tail to dig into the sandy seafloor, then secretes a slimy mucus that acts like cement to keep its burrow from caving in. When alarmed, garden eels withdraw tail-first into the holes they've created in order to avoid predators. Shy and cautious, they will slowly extend their heads out of the burrow once the danger has passed.