There is a free shuttle from downtown 3 times a week. Its actually a taxi service that gets reimbursed by Carrefour.
You need to phone to make reservation
Phone at least a few hours in advance 40-50-40-30
Days & Times of shuttle
Thursday 14:15 return pickup 16:30
Saturday 14:15 return pickup 16:30
Sunday 10:00 return 14:15
Sunday 14:25 return 17:00
Pickup is in front of the tourist office just before the ferry terminal. The car will be double parked there.
They often will drop you right at the marina gate if everyone onboard is from the marina