Hey now, I love Sealab 2021, but you have to know when to put down a dying dog. Harry Goz, the voice of Murphy, passed away during one of their best seasons and they had his son Michael continue doing Murphy until the season ended. The next season when they had him doing Captain Shanks and something definitely changed. It was like when Phil Hartman died and was replaced by Jon Lovitz on News Radio.
The chemistry was perfect when Murphy was on the show, same as when Hartman was on News Radio. Their replacements, while talented in their own rights, just could not keep up "the magic."
Now to compare Sealab to the Brak Show is not fair, they are different shows, they have different humor. That would be like comparing Futurama to Family Guy.
That is what is so great about Adult Swim, it is a veritable buffet of different comedy styles. Everybody gets something, therefore everybody wins.
...And I DON'T WANT to start a Family Guy vs Futurama discussion. Maybe in the next thread.