I am sure this is a sea squirt but do not have a clue what one and looking through all of the sea squirt records here there is nothing like it so not sure if this is invasive, sneaked in on the west Auckland current, native or endemic or not yet known so would like to know :)

Found washed up on the high tide mark on the south side of Pananehe, the island at Kapowairua. It is attached to a shell as can be seen in the photos.