South Beach sits on a sandbar with an ocean on one side and a bay on the other, and almost everything interesting about being on a boat here comes from that fact. The Atlantic is in front of your hotel. The working water, the flat water, the island houses, the sunset and nearly every dock are on the back of the island, a ten-minute walk away across three streets. Visitors who spend a week on Ocean Drive frequently never see it.
The dock that matters is the marina at the bottom of the island, on Alton Road near where the MacArthur Causeway lands. It is a genuine walk from the South of Fifth blocks, a short ride from 15th Street, and it is the reason a boat trip from South Beach is easier than one from the mainland: no causeway, no bridge opening, no mainland parking garage at either end. If a listing tells you to meet at Bayside Marketplace, that is downtown Miami, across the bay, and the boat will show you the same water from the other direction.
Immediately south of the marina is Government Cut, the dredged shipping channel between the tip of this island and Fisher Island. It is the reason South Beach exists in its current shape and it is the best thing on any of these routes: cruise ships and container ships transit it at close quarters, and from the deck of a small boat the scale of that is genuinely startling. You can also watch it for nothing from the jetty at South Pointe Park, which is what residents do on a Saturday afternoon.
Beyond the Cut the standard route runs the same way on almost every boat: north-west past Fisher Island, up the line of man-made islands off the Venetian and MacArthur causeways, a slow pass at Star, Palm and Hibiscus, and often a stop at Flagler Memorial Island, the small spoil island in the middle of the bay where boats raft up and people stand in the shallows. The narration on this route is a list of who owns what. Take it as scenery rather than as fact, because most of the houses are behind hedges and the guest list changes faster than the script does.
The one piece of timing worth planning around: the sun sets over the bay, on the far side of the island from the beach. A sunset trip from here puts the mainland skyline in front of you and the deco strip lighting up behind. It is the only reliable sunset over water this neighbourhood has.