Head on down to the docks at the bottom of the beach. Take out the two guards at the entrance and get to the end of the pier, taking out the four guards at the far end as you go. Now head over to the right and take out anybody you can on that side. Take out the last man and get in the boat.
Rush up to the yacht and start plugging at it with the on-board guns, ignoring the other boats. You should destroy the boat before they destroy yours, but it's going to be close. Keep a slight distance from the yacht to cause maximum damage. If it starts flaming, attempt to finish the job and jump out. Hopefully it will still explode. If you're having problems, get up to reputation level six, and buy the Cigarette Gun Boat and just bypass the whole pier and attack directly. You should finish it off in no time then.
You can now buy the hotel for $5,000,000. Try drug runs, plus the gangs in this area carry a lot of money. If you have Montana Holdings it will cost you $4,500,000.