I did like Roy Scheider as the captain of the sub and the stories were fairly interesting enough to keep me watching but overall the series was good but not great. I dont remember much of it these days.
Michael Ironside in Season 3 was good as well, but the struggle to decide where the series was headed killed it. In Season 3 it became darker and more like Star Trek under water. I do remember the Season 2 to Season 3 cliffhanger where the submarine was scooped up and transported to a water planet to fight in a war, but not much else. Season 3 picked up 10 years later after the sub returned to Earth by the aliens, explained by time dialation of near light speed travel. I think the time passage and darker themes turned alot of viewers off. Though I thought it made the series a little better.
I havent seen the series since it originally aired and I really dont care to see it again.