Hello everyone, I making this post asking for help with identifying this meiofaunal invertebrate I found from a sample brackish water from mudflats off of the SF bay. My first thought was "hey, that sort-of looks like a sea cucumber" but I don't think so anymore. In a few of the photos you can what very much look like cnidocytes, so I'm guessing this is some larval or polyp form of a cnidarian, but still I have little clue. I also captured this weird inflating thing it was doing with its "head". I'd appreciate feedback very much!