Nice touches with the free diving cave entrance and diving bell

The pirate in me is happy!
iserith said:
How would your players engage with this scenario?
Pick some pockets, make jokes at Falsetto's expense, and challenge the mercenaries to a drinking contest?
What would you change as DM?
I noticed you used a lot of
if the players do Y, then they gain advantage on Charisma check Z. On the face that looks fine, until you look at the specific examples: You help the merc's wounded...then you make a Charisma check (with advantage cause you helped) but on a failure they still treat you with derisive laughter and tell you to go take a long walk off a short pier... ? What the hell?
As a DM, I would instead not even call for the Charisma check and just let the PC's actions influence the mercs on their own merit. Calling for the Charisma check seems superfluous and threatens to invalidate the players' sense of agency in the game world. After all...what consequences really happen if the PCs FAIL the Charisma check?
For example, I'd leave out the hostile/unfriendly/friendly language and imply that if the PCs tend to the merc's wounded that means they're potentially strengthening a rival party. This gives the decision actual gravitas/potency without needing a die roll to give it "false weight." (Hope that makes sense, I realize I have my own gaming parlance sometimes) So it becomes a question of: Do we trust these Wild Hammers enough to help them? OR Do our values of helping others apply even to potential rivals?
What are some examples of exploration and social interaction challenges you have used in your game?
I haven't been DMing lately, but last year I successfully ran a structured
interrogation encounter in 5e (inspired by 4e's skill challenges) that played very well. Here it is:
http://www.enworld.org/forum/showthread.php?467592-Interrogation-skill-challenge-in-5e
What makes for a good challenge of this sort in your view?
I'd describe Dealing with the Wild Hammers as a
negotiation encounter, since the stakes are about gaining info/resources/access from NPCs. IME such encounters benefit from a minimum of dice-rolling. Some dice-rolling is fine of course, but the main outcome of the negotiation should be based on decisions rather than dice.