The divers brave jellyfish-infested water to test this prototype. I was afraid someone would got stung in the face. Also, did some jellyfishes got shredded at 0:11?
But, seriously, they're probably taking it out into more open waters and setting it up/inspecting it before tests. Probably a simple way of transportation. I imagine there was no warhead and it runs on electrical batteries, so it must be pretty safe.