Waves running up on a beach at an angle will push sediment along the beach. Longshore drift leaves markers as to the direction of sediment transport. Logs sticking out across the beach will have sediment piled on one side and the beach on the down drift side will be lower.
This log was holding back some well sorted gravel with two piles of gravel on the lee side of the log.
By the time I returned a half hour later the lee side of the log was completely submerged. By this point I was wading along the beach. Not much longshore drift was taking place on this calm day.