Bring a spring upon her cable Achievement in Turtle's Quest

Story related, cannot be missed,

A couple of cutscenes after landing. After talking to Jules (drunk guy near a rock to the far right) about turtles, head back to the dock for another long cutscene. You need to eavesdrop on a conversation between a group of people to the left of the docks. Walk to the front of the wagon, crouch down and walk under it. You will be prompted to listen. After another cutscene, this will unlock.