This mission is picked up after the mission, "An Old Friend".
After consoling a distraught Rosenberg, Tommy tells him their plan - to find the people responsible for the drug deal going sour, and then get payback. After a bit of thinking, Rosenberg tells Tommy of a retired Latino Army Colonel, Juan Garcia Cortez, who is hosting a party on his yacht, and every one of Vice City's power players are going to be there. He gives Tommy his invite, and advises that he gets a change of clothes.
Head to Rafael's in Washington Beach to pick up the Soiree Outfit, and then take the Freeway as a ride to the Vice City Marina to the south. Get there to activate the next cutscene.
Tommy is introduced to Colonel Cortez and his daughter, Mercedes, who tells Tommy the names of everyone on the boat - most notably, Avery Carrington, Jezz Torrent and eventually Ricardo Diaz, who arrives a little late. He is, as Mercedes puts it, Mr. Coke. To get away from the small loud-mouth of a drug baron, Mercedes wants Tommy to take her to the Pole Position Club nearby. Drop her off at the strip club to finish the mission.
Mission Passed: $100
The Soiree Outfit will be available from Rafael's, and Tommy's street clothes will be available from the Ocean View Hotel. Rosenberg will also still have missions available. You will also be seeing more of most of the characters you were introduced to on that boat.