Sandpiper

Today we tested the baby backpack that we brought (second hand) from New Zealand. Brilliant...young C seemed to enjoy it, and it's comfortable to wear. Passed as a success.
We went for a long walk along the beach, passing lots of holidaymakers enjoying the sun and surf, and also lots of incredibly bronzed individuals who tended to be of an older generation - resident retirees who spend all their time at the beach maybe?
Also along the beach were several species of shorebirds, species I am not at all familiar with. I think this is a sandpiper of some sort, (maybe semipalmated sandpiper?) - any help from knowledgeable birders would be much appreciated. Also saw a white egret in the surf - I thought they were normally found only in fresh water?