Worst murder plan or time-traveling idiot?

Tore Nielsen notes that a tv series about this bizarre murder case would be unethical. I’m just marveling at the #gameable possibilities.
Man crowdfunds and builds own submarine.
Journalist goes aboard, disappears.
Bits of journalist are found, it looks bad for submariner man.
….so if you wanted to kill a person, this would be the most traceable, least smart way to do it. If you can’t keep your story straight afterwards, it really looks damning.
So that’s merely crazy and tragic. But (here’s the gameable bit) what if he’s innocent?
What if there’s a rational explanation that is not the obvious?
Adventure writing prompt.
Bonus points for no Call of Cthulhu – remember, we’re avoiding the obvious.

http://www.bbc.co.uk/news/world-europe-40922750

A robotic blimp that can be stuffed through a 3.5-centimeter hole, unfold and inflate itself, and then explore large areas before deflating and escaping again

A robotic blimp that can be stuffed through a 3.5-centimeter hole, unfold and inflate itself, and then explore large areas before deflating and escaping again in being developed to go through a hole drilled in a sealed door of the Queen’s Chamber in the Great Pyramid, which might lead to a large void hidden deep inside the pyramid discovered using muon imaging.

“Once inside, the blimp is inflated with helium and unfolds to a diameter of 80 cm. It then undocks and floats off with a 50-gram payload of motors and sensors, including lights, cameras, and assistive navigation systems. Once its mission is finished, the blimp returns to its dock, deflates and refolds, and comes right back out the same hole.”

https://spectrum.ieee.org/automaton/robotics/drones/robotic-blimp-could-explore-hidden-chambers-of-great-pyramid