Here is the full list of all 16 Pirates: Golden tits: Chapter 1 achievements.
Visit a brothel 10 times
Finish 10 bounty hunting commissions
Spend 100 days sailing
Win an armwrestling tournament 5 times
Sink 10 ships
Listen to all of the Twig's poems
Fully upgrade your ship
Leave an uninhabited
Peek at the bathroom
Spend 20000 escudo
Beat Saint-Isidor bandits 5 times
Activate a cheat mode
Have a total of 10000 Escudo on yourself
Catch 50 fish
Touch Jaina while she's asleep
Journey Begins