Just 74 acres of nice grass facing San Francisco Bay. This is a beautiful place to fly a kite (it often has strong breezes), bike, or to just sit. Good for watching special SF Bay events such as the America Cup yacht races, 4th of July fireworks, Fleet Week Blue Angels, and the Escape from Alcatraz Triathalon.
One surprising thing is that there is still usually plenty of free parking here along the bay shoreline (except during special events such as those described above where the park is often used for event booths). This makes Marina Green Park a good place to start the Marina Walk or park before a walk to Fisherman’s Wharf.