The Berkeley Yacht Club holds Friday night sailboat races in the summer, and Cesar Chavez Park is a great place to watch them. A pair of binoculars would be a help when the contest goes way out toward the bridge, but at other times the boats come close enough to where you can see the sailors waving and working the ropes.
For a really close up view it pays to be on the southwestern point of the park, at the edge of the entrance to the yacht basin, after the race is over. With a due westerly wind, the boats can thread the needle between the two breakwaters and enter the harbor under full sail, like the Mojo, below.
Not related to the sailboat races but also coming into port at sunset was the Pacific Hornblower, part of the Hornblower dinner cruise fleet, which has a base next to the hotel on the north side of the yacht basin.
On the other end of the scale of vessel size, but not necessarily the scale of fun, was this group of three sailors in an inner tube, drifting a bit and paddling a bit in the middle of the yacht basin.