Oh dear, it looks as though I get to keep my gold stars once again. Jan was getting close with her thought of a bird's nest. What I had photographed was the entrance to a roosting pocket. I have a couple of these hung up but I haven't noticed them being used as a roost though the occasional Sparrow has briefly investigated them. The one I photographed was a spare which had been stored in the shed.
Right - I wonder how you will get on with this one. It is a small crop from a photo taken a couple of days ago with the Lumix. The camera is not waterproof so it is not a sea anemone. The red / pink part is, at the most, about 5mm across.
Very hard to think of a clue which doesn't give the game away. Let's just say I had to twist and turn to get a good view of it.
Many thanks as ever to those who tried to guess the last photo and good luck for this week. No prizes for a correct identification. Just for fun.