Increasingly popular are Milwaukee River (and occasionally Lake Michigan harbor) cabin cruiser tours, some also offering dining cruises.
The venerable Iroquois boat tours of Milwaukee Boat Lines (414/294-9450, www.mkeboat.com , 1 p.m. and 3 p.m. weekends, 1 p.m. weekdays June–Aug., $12 adults) departs from the Clybourn Street Bridge on the west bank of the Milwaukee River and offers scenic narrated tours. Sporadic evening tours are also offered June–September.
Rent your own as well but more, ahem, “social” sunset cruises (need an ID!) at Riverwalk Boat Tours and Rental (Pere Marquette Park, 414/283-9999, www.riverwalkboats.com ). This operation has a fave three-hour brewery tour taking in three local microbreweries on weekends ($25), along with a host of other public tours. You can also rent your own two-person boat ($15 per hour) or pontoon boat ($55 per hour).
At the Municipal Pier, south of the Milwaukee Art Museum , the replica 19th-century schooner Denis Sullivan is Wisconsin through and through, with all lumber culled from northern Wisconsin forests; it is more than 130 feet long with three 95-foot native white pine masts. Technically it’s a floating classroom, part of the new nonprofit Pier Wisconsin project, but its pricey tours ($25 children, $50–55 adults) are available to anyone interested in maritime history and ecology. They’re also jaw-droppingly spectacular, not to mention better-than-any-book educational. For sailing schedules, which vary year to year (and by season), call 414/276-7700 or visit www.discoveryworld.org/denisSullivan.php .
You can do it yourself by hopping aboard an old-fashioned trolley ($1) from Milwaukee County Transit System (414/344-6711, www.ridemcts.com ). Schedules have varied quite a bit, but service has generally been Wednesday–Sunday, summer only. Note that Summerfest , Brewers  games, and other sights outside the downtown are not served (the city has special summer shuttles for these).
Perhaps the most Milwaukee  way to tour the city would be aboard a rumbling Harley-Davidson. Organized group tours no longer operate, but House of Harley (6221 W. Layton Ave., 414/282-2211, www.houseofharley.com ) has the blessings of Harley-Davidson to rent brand-new motorcycles.