NCIS filmed Mark Harmon's Gibbs post-explosion survival in a way to keep all options open

TVLine

“We shot a lot of different things for that (sequence), and there were a lot of different ways to cut it,” showrunner Steven D. Binder tells TVLine of last season's finale. “And what we left with was something that we felt left all possibilities open. We know he’s not dead right there, and we know he’s able to swim well enough…. All things are still possible with Gibbs.”