For this tour, you leave from Le Touquet, where you park your vehicle. Take bus line 513 (Etaples - Berck) which passes, among other places, the covered market (in July and August, the market stop is moved to the corner of boulevard Dalloz and rue Jean Monnet, giving you the chance to admire the church and town hall and to feel as if you've crossed the English Channel).
The bus takes you to Berck in around 30 minutes. Go as far as the terminus, right next to the casino.
(S) Go to the sea via avenue du Général de Gaulle, then rue Singer.
(1) At the beach, turn right onto esplanade Parmentier. The walk continues on the GR®120, which is in fact entirely on the beach and will take you back to Le Touquet.
At the start, you pass 2 helio-marine institutes, Berck being renowned for its motor education and specialized care centers for disabled children. Pass Merlimont beach before Stella Plage.
(2) Continue along the beach to Le Touquet.
On your right is the Thalasso centre. You're almost there. The sailing and kite surfing school marks the end of the beach route. All that's left is to go back up the Boulevard de la plage ("Beach Boulevard", what an original name) and find your car (E).
Note for this outing: It's impossible to get lost, just follow the coastline.