Although public awareness of the marine environment has grown significantly since then, the customs officer's attitude towards barnacles is still a common one. The barnacle's habit of growing on almost anything in the ocean, from rocks to whales to boat hulls, can be not only annoying, but also expensive. In less than a year the number of barnacles growing on a large ship can cause enough drag to increase fuel consumption by 40 per cent. In less than two years, a large tanker can accumulate more than 10 tons of barnacles. Removing their hard calcareous shells is time-consuming and expensive.
Barnacles are crustaceans related to shrimps and crabs.
Although the volcano-shaped shell of an adult barnacle does not resemble an adult crab or shrimp, the juveniles, or larvae of barnacles bear a strong resemblance to other crustacean larvae. Barnacles, like most crustaceans, spend at least the first few weeks of their lives as tiny planktonic larvae, swimming and feeding near the surface of the ocean. They pass through a series of moults until they reach a stage where they are ready to attach and assume the adult form. Once a barnacle larva finds a suitable surface to settle on, it secretes a strong adhesive from glands on its first antennae, glues its head to the surface, with legs extended above, and starts to create a hard outer shell. The glue used to attach barnacles is one of nature's most incredible adhesives.