In [#103 Thirty Days], the Delta Flyer travels into a spaceborne ocean.

Events are portrayed in flashback, recalled by Paris while in the brig serving 30 days' detention after being demoted to ensign.

The Delta Flyer dives into the ocean. (pop-up window)

Voyager encounters a contained ocean in space which resembles a planet, owned by the Monean Maritime Sovereignty whose ancestors discovered the world 300 years ago. The Monean consul and his aides are invited aboard Voyager and first contact is made. Because the Monean called Riga says that research vessels are unable to investigate the ocean's centre because their best research vessel cannot penetrate the ocean further than 100 kilometres, Paris suggests that the Voyager crew take him. Paris claims to Janeway afterwards that with a few simple thruster modifications and immersion shielding the Delta Flyer can be made seaworthy in no time. By contrast, Janeway says that it would take a week to make the same modifications to Voyager.

As Paris, Kim, Seven and Riga dive into the ocean in the Delta Flyer (pictured), aboard Voyager Janeway informs the Monean consul that, upon running a computer simulation, it is estimated the ocean will suffer complete loss of containment in less than five years. Paris, Kim, Seven and the Monean called Riga travel into the ocean surface in the Delta Flyer to investigate the ocean centre. They travel past the Monean underwater city and its refineries (pictured). At 600 kilometres beneath the ocean surface they discover an alien reactor over 100,000 years old (the screenshot shows a close-up view as seen through the front window of the Delta Flyer), and determine that the Monean world was actually formed using a kinetic transfer system to draw the water around the reactor. The Delta Flyer crew determine that it is the Moneans' mining operation that is destroying the ocean by extracting oxygen from the water, forcing the core to transfer power from containment to keep from being crushed by the added density of the ocean. While investigating the ancient reactor, an encounter with a sea creature similar to an electric eel results in the Delta Flyer's thrusters going offline and the Delta Flyer's shields end up "fried" as the result of the creature generating over 500,000 volts. The hull breaches and water leaks in. They lose communications, shields and propulsion. They reinforce the reactor's stability with a power transfer although it can only be a temporary measure. The measure renders it unnecessary for Voyager to reinforce the breach in the containment field with a deflector beam. To reduce the Delta Flyer's density and thereby float to the surface, they vent plasma and transport all non-essential equipment off the ship.

the sea creature generates electrical current which fries the Delta Flyer's shields

Back on Voyager, Janeway offers the Monean consul several long-term solutions which would render the refineries obsolete but the consul intends only to suggest them in a subcommittee report. Riga and Paris believe the Moneans will take no action. Paris feels so strongly that he disobeys orders to disrupt the Moneans' internal affairs - he and Riga commandeer the Delta Flyer and go to take the oxygen refineries offline. The unauthorised launch of the Delta Flyer from shuttlebay 1 is immediately noticed. When Paris refuses Janeway's repeated orders to desist, she orders a photon torpedo readied which Tuvok converts to be used as a depth charge. Once they reach the reactor, Paris launches a torpedo at the same time that Voyager does, and the two torpedoes meet and explode just short of their targets.

The Delta Flyer and its occupants return (not seen on tv) and Paris is punished by demotion to ensign and 30 days' solitary confinement in the brig.