We used to dig up cockles & use salt to capture Razor Clams as students.
Today I took my 3 year old daughter to do the same thing.
She absolutely loved it and got ridiculously excited when the razor clams appeared of of the sand, through the salt.
We used a rake to dig up the cockles and then scoured the beach for the caracteristic holes in the sand that tells you where the razor clams live.
You just add salt to any likely dents or holes in the sand. If a razor clam is present they normally squirt at first, then slowly emerge from the sand. When they are poking out enough, you have to grab them quickly and slowly ease them out of their holes. Do it too quickly the foot (the bit you eat), can get snapped off.
We cooked the cockles and razor clams, there and then, with a portable camping stove and then ate them.