In the documentary of his record-breaking deep-sea dive, "Deepsea Challenge 3D," James Cameron asks, "Am I a filmmaker who does exploration work on the side, or am I an explorer who does filming on the side?"

It's a good question. It's now been five years since Cameron's last feature film (a little independent movie called "Avatar"), and in that time, the priorities of the most bankable director in Hollywood have sometimes been as murky as the deep sea.

He has spent those years producing a fleet of documentaries about ocean exploration and deep-water life forms. His biggest project hasn't been a mega blockbuster but building a deep-diving sub and piloting it more than 35,000 feet down into the Challenger Deep, the deepest part of the Mariana Trench.

"I make the Hollywood movies to pay for the exploration," Cameron said in a recent phone interview from California.

Certainly, many moviegoers are eager for Cameron to get back on a film set. After some earlier postponements, he's on his way, currently finishing the scripts and design work for three planned "Avatar" sequels.

But for now, on Friday, he's releasing in theatres a 3-D film for National Geographic that chronicles his 2012 dive into another alien world, "the last great frontier," as he calls the ocean. For Cameron, the movie is a testament to the spirit of exploration, which he feels is flagging in America.

Cameron's dive, nearly seven miles deep, was only the second manned-dive to reach the bottom of the Challenger Deep, the deepest known point of the seabed. Some 68 new species were identified from the sub, which was equipped with 3-D cameras.

"I think explorers feel a sense of the sacred," said Cameron of descending into such a remote abyss. "Something that's beyond themselves, when they go to a place that's never been witnessed before and bare witness for the first time."

"Deepsea" co-director John Bruno had to capture it all in stormy conditions and while co-ordinating 3-D cameras that each took two men to operate.

"The ocean hasn't read the script, so it's not going to co-operate," says Cameron. "And the sub is a bit like a diva movie actress. You're not always going to get it on camera when you want it."

The similarities of leading an expedition team and a feature film crew are, to Cameron, identical. Ever the taskmaster, the documentary shows him prodding his scientists on their time tables. In Cameron's day job, the interaction would be the same.

Speaking of time tables, there is the pace of work on the "Avatar" films, which are scheduled for release in 2016, 2017 and 2018. Though Cameron earlier said the screenplays (which he's writing with Josh Friedman, Rick Jaffa, Amanda Silver and Shane Salerno) would be finished by the end of the spring, they're still being completed.

"It's going to be another couple months, I would say, at least," said Cameron. "We will serve no wine before it's time, and I would be pretty stupid to run off and start shooting 'Avatar' until the scripts are perfect. Whether that compromises our announced release date of Christmas '16, at this point I can't really say until we break down the budget and schedule."

Cameron said he's working seven days a week on "Avatar" as the pages "pour in," but with one exception. He's taking an upcoming vacation to Tahiti for -- what else? -- a little scuba diving.