A nuclear submarine crashes outside the station, and the crew of Sealab (in a rare occurrence) must work quickly to stop an environmental disaster from happening.

As Captain Murphy leaves for The Great Spice Wars, a new captain, Tornado Shanks, is given the helm.

The last of Captain Shanks' brothers (who are all named for mythical Greek heroes) dies from a heart attack while taking a dump; all the while, Hesh and Debbie Dupree get married.

Dr. Quinn teaches Debbie Love's class of 4th-graders including Fatass McBlobbicus, while having to deal with Tornado Shanks' warped and unscientific view of education. The classic story "The Scarlet Ibis," by James Hurst, is ripped off as part of a classroom discussion of death. All the while, cuts are made between Debbie Love's classroom and the spa Love is visiting, creating a series of double entendres.

Hollywood Actor Beck Bristow (Brian Bloom) comes to Sealab to study for a television role.

As it turns out Sealab was built on an ancient Indian burial ground and is now sinking into the ocean floor. The only hope to save Sealab is John Bear, Sealab's resident Native American. But in order to save Sealab Shank's must agree to turn the Mess Hall into a casino which he does. But once the casino opens John Bear still won't stop the sinking (or let Debbie have a lounge show).

Marco's illegitimate son applies for a job on Sealab. Can he pass the civil service exam with Debbie and Quinn helping?

The cast looks back over five years of "A Legacy of Laughter" in the style of one of those tacky TV reunion specials but of course since this IS Sealab, not all goes well.

Quinn and Stormy are stuck in a cave with only 10 minutes of oxygen while sealab burns.

A delivering mishap and some dishonesty on Sparks' part pockets Sealab a brand new Asteroid Smasher/High-definition Television. Unfortunately, the ASHDTV was supposed to go to Spacelab so they could destroy an asteroid hurtling towards the earth.

Abalon, a terminally ill whale, comes to Sealab and asks Doctor Quinn to kill him. While Quinn wonders whether or not he could end a life Stormy recognizes Abalon as the star of a show called ‘I Gotta Have That Dick' and starts bugging him with fan fics. While Quinn examines Abalon's whale cancer Marco accidentally eats some of it and is inspired to create his own drink called F-YEAH!

Dr. Quinn forcibly takes a well-deserved vacation, inside Sealab's walls, the crew attempts to find out what he's doing.

Debbie and Quinn break up, while Dr. Virjay gets his old rock band back together.

Captain Murphy opens Sealab to tourists, eventually prompting Dr. Virjay to renounce his religion, and begin to eat meat from cows.

Quinn, White Debbie, and "He Who Smokes Bitches" Stormy Waters venture deep into Tornado Shanks to destroy a malignant tumor in Captain Shanks' head.

Tornado Shanks declares Sealab a sovereign nation in order to be his own tax haven. A wave of secession fever sweeps through the entire crew, with a half-dozen nations declaring themselves independent in a few minutes; with the help of two British businessmen, they are all soon armed with missiles allegedly loaded with nuclear warheads. When push comes to shove and every Sealab nation declares war on every other one, however, the nukes all turn out to be duds.

Zombies ravage Sealab as Debbie plans her (fifth) 30th birthday party.

Marco died three episodes ago. What's he doing back? Later, Marco and Debbie sing Antônio Carlos Jobim's "Waters of March" in Portuguese.

Murphy's golf game is, due to a lack of golfballs, cut short. Murphy embarks on a frantic quest to find the Pro Shop. On the way, Murphy runs into a Monster-Hesh, snotty telephone operators, the Dolphin Boy, and a perfidious Eggers.

Stormy's meddlesome inquisitiveness uncovers Shanks' membership in a world-controlling society.

A grief counselor tries to help the Sealab crew through a hard time.

Marco convinces Debbie to give up her "questionable" ways through a pep talk, leading her to find religion and dump Quinn. Meanwhile, Sparks recognizes the pep talk from a 60's show, which leads a drunken Quinn to sic the network on the fugitive TV star Marco.

Extreme rebel trillionaire, Max Stone, buys Sealab and ends up running it better than before.

All the water around Sealab has disappeared, and left Sealab high and dry. Where has it all gone?

A network executive audits the set of the hard-hitting action drama Sealab 2021, with hopes of somehow salvaging the dwindling series.