Compared are the Theatrical Version, represented by the official US DVD by Universal, and the US DVD von GoodTimes (not rated).
Besided the usual Theatrical Version, a slightly extended version has been released in the US as well. This version is not rated and the only extended release worldwide. All other releases only contain the regular US Theatrical Version. Even the US VHS with the note "Contains New Footage Not Seen In U.S. Theaters", similar to the DVD by GoodTimes, on the front cover, only contains the regular Theatrical Cut. The new footage is quite irrelevant, it is just supposed to increase the tension during the showdown. Even though the new footage fits perfectly well, it doesn't change the actual movie at all. That's why one can say the release of this version doesn't make any sense.
The time index of the extended scene refers to the Theatrical Version.
The remaining difference in running times is a result of the rounding of the running time to a half/complete second.
Running time Theatrical Cut: 1:29:57 min (1:26:01 min credits excluded)
Running time Extended Version (not rated): 1:30:43 min (1:26:47 min credits excluded)
1 extended scene = 45 sec
After Jake (Mario Van Peebles) has been eaten by the shark and Michael went below deck, the Extended Version contains several added scenes. Helen directs the boat and Hoagie tries to stem the water in the engine room while the shark is moving behind the boat. The shark stays there for a while and follows. Then a shot from the shark's point of view to sneak a peek at the boat, then the shark vanishes by diving.