Vieux Port to Port Lympia in one hour along the whole Riviera. No A8, no transfer.
The A8 across the entire Riviera is saturated all summer, and there is no direct train from Saint-Tropez — you first have to reach Saint-Raphaël by road.
1 hour dock-to-dock, Vieux Port to Port Lympia. Pass Cannes, Antibes and Cap-Ferrat from the sea and step off in the heart of Nice.