Usually when we decide to go to the beach I check the tides and find it is high tide so we postpone until the next week, then forget to go. But today I checked the tides and found that low tide was only 5 minutes away so we jumped into the van and headed down. It is a lovely day today, calm and mild, and not many people on the beach. We hauled a whole lot of kelp up the hill for the vege garden (that was a bit of an effort). Washed up on the beach were quite a few small plastic-looking barrel-shaped things, some of which had a creepy-crawly inside that looked like it could be a baby crayfish or something.
When we got home we looked it up and found it was a creature called Phronima. It is a parasitoid which finds a salp (something else we'd never heard of, apparently a "barrel-shaped, planktonic tunicate") and eats its insides out then lives in the clear plastic-like shell, where it also lays its eggs.
The kids also found a spiny centipede-ish sort of thing which we haven't been able to identify at all.