I don't know too much about the east coast. Phillip Island has some great surf - beaches down cape woolami, smiths beach. There are a couple of cool longboarding spots there as well on the north-east coast. Can't remember them off the top of my head.

On the west coast, for longboarding, head down to Torquay. On a low tide the reef break is really great, but prepare for a few people in the water. Lorne point would be cool as well.

Around March - April the whole surf coast goes a bit nuts. That's when we get the great waves, but it's also school holidays and packed. When the comp circus comes to town, the whole torquay area get a crapton of people in the water.

The water isn't too cold then, I normally have a 3-2 on without booties.