Pirates are not known for their cleanliness. By-and-large, they just don't care for bathing. So how do you convince them? Offer a soap that smells like spiced orange and rum.
You can also pack that soap full of activated charcoal powder - which will have the detoxifying effect of soaking up excess dirt and oil. Tell them that the soap is blackened with the evil souls of a thousand pirates past, and they'll like that even more. In reality, of course, the charcoal is made from coconut husks (very sustainable), but they won't know that. They're pirates - not a lot of doctorates in the crowd, you know?
That works well with the coconut oil base of the soap. Pirate likes coconuts. This is like Pirates 101 guys. Come on.
And if you really want to clean those suckers up, take finely ground pumice powder and mix it into the soap base. That's going to exfoliate that nasty pirate skin and get em cleaner, let's face it, than they've ever been.