Re: It's easy to get hydrogen from seawater... NOT
By that thinking, it is also easy to convert hydrogen to helium - clearly possible, and done on unimaginable scale every day - but that is not necessarily what the robot guys had in mind now, is it?
Converting electricity to hydrogen and that in turn into heat seems like a dumb idea even to me, since there are much simpler ways of creating heat from electricity.
Thus, the way I would understand what they are trying to do is to simply collect ambient molecular hydrogen from the ocean and use that to drive their system, though they might be better off trying to convert ambient methane to hydrogen and use that.
(for more info see: "Methane and hydrogen in seawater (Atlantic Ocean)", Deep Sea Research Part A. Oceanographic Research Papers; Volume 35, Issue 12, December 1988, Pages 1903–1917)
gotta love internet search engines....