With Deb still impulsively driving Dexter's car into a lake in an attempt to take both their lives after her discovery of Harry's actual cause of death, the final moment could have been slightly longer if an additional filmed scene was added. In the deleted scene, Deb valiantly pulls Dex back to land then attempts desperate resuscitation with CPR and mouth-to-mouth followed by a cut to black.
It seems the aired ending was a slightly more powerful conclusion with an abruptness that signals how dramatic Debra's regret was and with how much despair the rescue effort transpired.
Would you have preferred the additional scene be added? Perhaps the producers decided to make it the beginning of the next episode if it picks up at the moment "Scar Tissue" concluded. It may possibly be included as a bonus feature on the season 8 DVD/Blu-ray if not.
Personally, a cut to black after the car is submerged in water would have been a more powerful ending for me that would have created a real tension for next week although I can see why the writers wouldn't leave the fates of both characters (although only Debra could realistically die before the end of the season) so much so in the air.
Looking through behind-the-scenes photos from the set's initial filming, I was able to find an image (above; albeit low-quality) of what would have originally ended the episode.
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