S01E51 - Artemis of the Transparent Sea (1)
Synopsis
As the 999 approaches its next destination, a large number of small blue blobs start passing by the 999, warning it to not go any further. Eventually the 999 gets stuck in a larger version of these blobs, which apparantely is their mother. The Galaxy Railways headquarters gets ready to blow it up so the 999 can go on, but all of a sudden a ship crashes into the blob.