Why "whale"? Historically whales were found on this spot. Dead mammals were studied even by Pliny the Elder, a famous Roman naturalist of the first century. From above it is visible that the whales could get stuck on the shore at low tide.
There is a huge sandy Conche beach near the lighthouse. Consider that the beach is wild, without any infrastructure.
Getting there: a large free parking N 46 14.515 W 1 33.338. If you go only to the beach, then it is better to park here N 46 14.539 W 1 32.442. From La Rochelle you can take the bus 3/3E, find here a link to the current schedule.