Lucky enough, we were at the estuary of Mordialloc and the river was filled with boats. It's not a big place, but we felt it was such a lovely scenery - of boats, river, timber platforms, some nice breeze and the sun. Somewhat 'luxurious' scenery I would say, and a nice change from looking at city buildings all week long. We were reassured that the scenery was a great one because we even spotted people taking their wedding photos there!
Mordialloc is about 45 min away from Melbourne CBD. Free parking for 2 hours is on the other side of the river near the boat clubs and houses (where we took these photos), but otherwise, paid parking spaces are plenty. You can come for a picnic on the lawns by the beach - they are pretty similar to those along St. Kilda Beach.
p/s: You can even hire the boats.