How do you get ancient pirate coins in sea of thieves?

Excuse me, I'm a bit intrigued by the concept of acquiring ancient pirate coins in the game "Sea of Thieves." Could you possibly elaborate on the steps one must take to acquire these elusive treasures? I'm particularly interested in understanding the methods players employ to unearth these valuable coins, whether it's through solving puzzles, defeating enemies, or perhaps some other creative means. Additionally, I'd be grateful if you could shed some light on any potential challenges or obstacles that might hinder the process. Thank you for your time and assistance.