it is a 5 minute walk.
You're a bit of a slow walker Brian!!
The bus service is designed to connect with the ferry. You'll have plenty of time for lunch as well if you didn't eat on the ferry. Subway is just a short distance from the ferry.
Brian will have jogged into down town Picton and back :)
Google says 4 minutes/ 300 metres. I haven't done it by bus since 2006 when I stayed overnight in Picton anyway. Knew it was just along the road.