Barnacles can cut you pretty badly if you're not aware of them, and they have a habit of reproducing. When you have a large colony on the hull of your vessel th

Barnacles can cut you pretty badly if you're not aware of them, and they have a habit of reproducing. When you have a large colony on the hull of your vessel they impose a nontrivial amount of drag. (I'm more committed to the bit than this position though, it's a judgement call that an engineer must make relative to the requirements and resources available.)