The Bonny banks of Loch Lomond in just over an hour with beautiful Inchcailloch island accessible by boat
This on the old Glasgow road and is a good stopping place if you are coming round the mountains to get to Dunoon rather than crossing the Clyde estuary. It has a shop and cafe, Toilets etc.
Shimmering Loch Lomond is a 20 minute drive from Glasgow. Boat trips can be booking on loch.