What craft did the strongest pirate groups use?

Did pirates use modern motor launches, and which group fielded the most formidable vessels?

The Bias Bay pirates were among the strongest, but tended to use adapted local craft because motor launches stood out.

The Bias Bay groups were the focus of the largest British operations. Their vessels were more often adapted local merchant craft than conspicuous purpose-built motor launches. Blending into ordinary coastal traffic was more useful than advertising a specialized pirate platform. Modern launches would also have been easier for patrol forces to identify. The answer links material choice to concealment and local operating conditions rather than assuming that the strongest group owned the most technologically advanced craft.