It's afaik the only glider type UUV (ed: being looked at by .mil. and production intended. and bigger than the research gliders by far.), afaik. Which is super interesting in itself, for endurance purposes. But perhaps this depth-changing mission profile is also key to its energy harvesting?

Just guessing here, but... it's sinking and rising. Well, perhaps it can take some mass of water onboard & run temperature differential energy harvesting off that. Take on warm surface water, slowly glide down 1000 ft (while going much further forward), then run a thermo-electric generator against the cold deep. Swap water & take 300 gallons of cold water, glide up 1000 ft (and forward), then run a thermoelectric generator against the warmer surface water or the air and/or solar. Repeat ad-infinitum. No idea what kind of power you could pull here but maybe, and it fits with the glider core concept.

And yeah, maybe if you do find an underwater vent you can supercharge? :)

Shout out to The War Zone (TWZ)'s coverage over time. The recent is decent but links their previous which looked about some. https://www.twz.com/news-features/manta-ray-underwater-drone...

TWZ talk about something mentioned elsewhere in the comments, yes, the data-linking challenges are partly tackled by having a "data bubble" that can float to the surface & uplink, who knows, maybe downlink relay too (unspecified). I definitely want to imagine the data bubble as a recursive system, as itself a smaller glider drone, but I'm 100% making that up, is my sci-fi impulse.