What is better than a free cruise? Nothing else. However, its range is quite limited since the tour only lasts for two hours (it turns around before reaching the Sailing Club marina), but you can't beat free right? (Compared to around $100 normally)
The opportunity for free tours was first available sometime in June, but I didn't see it until reading the newspaper article about it. By that time all of the free cruises that were available (up to end of July) were sold out, that's how popular it is. But not to worry - they're doing more cruises for September starting in a couple of weeks.
Protip: They make available 3 cruises per Saturday, 10am, 1pm, 4pm, for 50 passengers for September starting on August 5 at 8am. If you were unable to get a reservation or can't wait that long, you can always wait in the standby line. Arrive around 45-60 minutes early for an almost guaranteed first priority on standby (if someone fails to attend, and it is almost bound to happen, you can go). If that doesn't work, you can call them up to (most likely) get higher up the priority line for the next cruise.