It seems I had to dig with my back to the sea. That way I used the shovel to prevent the clam from making its way to the ocean through the water-loose sand with the tide even as I was digging. Turning my back to the ocean went against everything I had ever learned about playing in the surf. Ken laughed at my concern, though. You won't get any the way you're digging.
Wounded pride is a powerful incentive.
I set my jaw, grabbed my shovel and waited for the next wave to reveal the little holes which would lead me to the treasure. Lunging towards the nearest one, my back to the ocean, I stabbed my shovel straight down as deep as I could. Prying back with all my might, I flipped the whole shovelful out on the wet sand. There, sure enough, was my first clam. This was just the beginning.