What’s with the CG in Lost?

There have been several sequences, few and far between in Lost that involve entire CG renderings that look horrible. Two that stick out in my mind the most are the submarine dive sequence from Season 5, where the vessel literally looked like it was pulled out of a late 90’s computer game. Last night’s underwater sequence took the cake though, the camera panning, cheesy music, and terrible rendering was a total buzz kill.
It’s obviously not budget, ABC has the money and Lost is one of the top viewed shows on television. Lost’s creator J.J. Abrams has plenty of experience with great CG in his films Cloverfield and Star Trek. So what is it?