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Why do tunicates grow on ship hulls and wharf piles?

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Bright blue sea squirt Rhopalaea crassa with yellow-edged openings grows on a coral reef among various corals in the Philippines. — tunicate Blue spot sea squirt (*Clavelina moluccensis*), a colonial tunicate.

Sessile tunicates grow on ship hulls and wharf piles because they require solid surfaces for attachment during their adult life stage.1

The life cycle of these chordates includes a brief, motile larval phase, during which the larva swims to locate an appropriate substrate. Upon finding a suitable surface, the larva uses adhesive papillae to attach itself before undergoing metamorphosis into its sessile adult form. Because they occupy these man-made structures, some tunicates are classified as fouling organisms.234