Regarding skill checks. The percentages I list worked for me. Higher percentages will give you a greater chance of passing skill checks the first time. A quiet two-note tone will play every time you pass a check. IMPORTANT If you fail a skill check immediately dashboard then quit the game. Reload the game and you’ll be restarted from the last checkpoint. If you’re not fast enough then the option will be gone forever and you’ll be locked out. Since inventory and items do not carry over you'll have to restart the game If you do have to reload be sure to pick up all collectibles that did not save.
Deliver the liquor to the 2 (drunk) sailors near the 2 warehouse guards. You'll find them once you cross past the dead killer whale. Speaking to the harbormaster Fitzroy opens the way.
First speak to the drunk sailors, then to the bootleggers blocking the path. Return to the drunks to have the dialogue option to get rid of the two guards.
Walking away from the drunk sailors towards the statue of Saint Brendan (near the ocean) you will pass three identical small huts on the right. Pick the lock of the first hut you come to and pick up a bottle of liquor. The beginning skill levels (Investigation 40%) will pick the lock and (Spot Hidden 30%) will find the booze, this worked for me, others have reported it didn't for them. Return to the drunk sailors and give them the bottle, they will lure the guards away.
There is another option to buy a bottle of whiskey from the bartender. You'll need higher eloquence and doing this will not give you progress toward the hidden items achievement. So this is not recommended.