18th century Caribbean and European piracy: what did pirate ships look like, and how did most acquire their ships?

Admittedly I have a very Hollywood view of piracy in the 18th century. I have the image in my head of two very large ships, one with the Union Jack flying above it and another with a Skull and Bones flag.

Was piracy really like this? If so, where would a pirate crew get ahold of one of these large and expensive ships?

Or was it more akin to modern day piracy where they had smaller, faster, skiffs that caught up to the big ships?