Barnacle?????

Barnacle?????

Observation - Barnacle????? - UK and Ireland. Description: Lots of these on the tide line this morning attached to each other not on any solid object. Thin plastic like shell with feathery antenna. Help with id needed

Lots of these on the tide line this morning attached to each other not on any solid object. Thin plastic like shell with feathery antenna.
Help with id needed