Editing Sipuncula (section)

==Distribution and habitat==
[[File:Sipunculus nudus.jpeg|thumb|left|''[[Sipunculus nudus]]'']]
All sipunculid worms are marine and [[Benthos|benthic]]; they are found throughout the world's oceans including polar waters, equatorial waters and the [[abyssal zone]], but the majority of species occur in shallow water, where they are relatively common. They inhabit a range of habitats including burrowing in sand, mud, clay and gravel, hiding under stones, in rock crevices, in hollow coral heads, in wood, in empty [[seashell]]s and inside the bones of dead [[whale]]s. Some hide in kelp [[holdfast (biology)|holdfast]]s, under tangles of [[eelgrass]], inside [[sponge]]s and in the empty tubes of other organisms, and some live among [[fouling]] organisms on man-made structures.<ref name=Pancucci/><ref name=Walls/> Some bore into solid rocks to make a shelter for themselves.<ref name="Nguyen Thi Thu"/>

They are common below the surface of the sediment on [[tidal flat]]s. These worms may stay submerged in the sea bed for between 10 and 18 hours a day. They are sensitive to low salinities, and thus not commonly found near estuaries.<ref name= "Nguyen Thi Thu"/> They can also be abundant in [[coralline rock]], and in Hawaii, up to seven hundred individuals have been found per square metre in burrows in the rock.<ref name=Ruppert/>