Saint-Valéry is the bay's departure point. Boat trips run out into the estuary from the quays, guided walks cross the sand towards Le Crotoy on foot at low tide, and nature guides run seal and bird outings from a kiosk beside the marina.
Everything here is governed by the tide, which comes in across the flats faster than most people expect — which is exactly why the crossings are guided rather than a thing you do on your own with a map.