The inventor David E. H. Jones, better known as Daedalus, described a very similar underwater glider in one of his columns. From memory, his version exploited a liquid that changed volume with temperature, rather than a wax (and the temperature-volume relationship was in the opposite direction).
The column is included in the compilation "The Further Inventions of Daedalus" published in 1999. I think an early prototype of the wax-based mechanism (apparently an independent, though later, invention) had already appeared at the time of publication.
It's astounding how many of Daedalus' crackpot schemes later emerged as real inventions -- occurrences Jones documents with enthusiasm in the two compilations. One great example is the similarity between Daedalus' "Unisphere" and the much later Segway.
I go on working for the same reason a hen goes on laying eggs. -- H.L. Mencken
