From the Gabriola ferry terminal, Gabriola Sands Provincial Park is reached by turning left onto Taylor Bay Road and following the signs. The BC Ferries crossing from Nanaimo takes about 20 minutes, so most of the trip is the sailing itself.
The crossing from Nanaimo
BC Parks lists the ferry from Nanaimo to Gabriola Island at roughly 20 minutes. Sailing times shift with the season, so open the BC Ferries sailing schedule before you head to the terminal, and check there whether your date needs a reservation for a vehicle. Foot passengers and cyclists have an easy time of it, since the terminal sits close to the road you need.
Taylor Bay Road to the isthmus
The park sits on the northwest side of the island, on an isthmus between Taylor Bay and Pilot Bay. BC Parks gives the directions this way: from the terminal on Gabriola, turn left on Taylor Bay Road and follow it until you see signs for the park on Decourcy Drive. A map app on your phone helps at the junctions, and signal can be patchy, so load the route while you still have coverage on the ferry.
The park page does not give parking details. If you drive, look for the BC Parks notice for current guidance, or call the park operator, RLC Park Services, on 1-250-474-1336.
Bring what you need
Gabriola Sands is a day-use park with no drinking water, so pack your own. That matters on a warm beach day, and it is easy to forget when you are focused on the ferry.
Rides on the island
Taxi service on a small island can be thin, so arrange a pickup in advance. The Gulf Islands taxi page covers rides around the islands, and the taxi fare estimator gives a rough idea of cost. If you arrive on foot or by bike, ask locally or look online for current rental and shuttle options, since those can change from one season to the next.