Here's one of four individuals that I encountered on 11 May 2016:
Did you notice the small pelagic barnacles (Lepas sp.) attached to the outer whorl of this snail? We had heard that Lepas sometimes attaches to Janthina, but we didn't see this ourselves until April-May.
Here's a view of a snail shell floating at the surface, with the attached barnacles hanging below (their feeding appendages are extended like fans):
Although they start out small, these pelagic barnacles can grow to a size much larger than the snail. Do the barnacles eventually weigh down the snail? Does a snail have to add more bubbles to its raft to counteract the barnacles? (For a picture of a bubble raft, review the post from 20 January 2016.)