PORTSMOUTH — The public rarely encounters an offshore oil rig unless there’s a spill or industrial accident and images of these massive environmental blights are published by the news media.

On Thursday, Nov. 21 at The Music Hall Loft, in Portsmouth, marine scientist Emily (Callahan) Hazelwood, a 2007 St. Thomas Aquinas High School graduate and Seacoast native who grew up in New Castle and North Hampton, is going to ask the public to look below the surface and take a deep dive into the environmental impact of oil platforms and other massive industrial structures built in blue ocean environments.

Her conclusions will likely surprise you.

Hazelwood on Thursday will present the short documentary “Transecting Borneo,” which explores the marine ecosystems that grow on and around oil platforms and asks whether it is better for the environment to remove oil rigs when they stop producing or to leave them in place to serve as artificial reefs.

Under the right circumstances, Hazelwood said, it’s better to leave them in place.

“What you see from above the surface could not be any further from what you see below the surface,” Hazelwood said. “What makes them unique is more often than not they are in a blue ocean setting far away from near shore runoff, erosion and issues like that, so they create these little refuges for marine life. Further, they’re massive. Some of the biggest ones are taller than the Empire State Building, so you have a lot of real estate for marine life to grow and colonize on. They’re quite complex with lots of beams and cross beams and marine life is very attracted to that because it provides nooks and crannies for them to hide in and eventually they’ll reproduce.”

The film explores one converted platform in Borneo but there are more than 2,000 rigs in operation across the globe and Hazelwood noted there are oil and gas rigs, wind farms and other massive industrial structures in all the world’s oceans.

Hazelwood, daughter of Exeter Hospital President and CEO Kevin Callahan (who makes a cameo appearance in the documentary), is a co-founder of Blue Latitudes and the nonprofit Blue Latitudes Foundation. She and her partner, Amber Jackson, work with governments and oil companies to analyze whether a decommissioned rig is suitable to become an artificial reef and to educate the public about the biodiversity and abundance of marine life that quickly populates the rig’s support structure.

“It’s very counter-intuitive,” Hazelwood said.

Marine life is attracted to hard substrate, such as reefs, which are rare in the world’s oceans. Hazelwood said marine life grows so quickly on blue ocean platforms that while they’re in operation oil companies need to sand blast them every five years to remove the marine life that creates drag in the water column and could make the rigs unstable.

When a platform comes to the end of its economic life oil companies can remove it, which is extremely expensive, or they can reef the rig, which costs about half as much and, Hazelwood said, in many cases actually has less impact on the environment and a lower carbon footprint. Rigs can be turned into reefs by one of three methods. They can be towed to a reefing area, they can be toppled onto their side or the top 85 feet can be removed to allow ships to draft over them.

“At this point not every platform is a good candidate, but for those that are we can absolutely say that they are producing marine life and they are good habitats for life,” Hazelwood said. “In California they have been found to be among the most productive ecosystems on the planet.

Because the concept of turning rigs into artificial reefs is a relatively new concept, there are some hard questions being asked about the risks to the environment.

Critics suggest that the man-made rig structures contain toxic chemicals that will be released as they decompose and that it would be better for the environment to remove them. There are also concerns about whether they attract invasive species into blue ocean environments. The fishing industry has concerns about their impacts on trawling. And there are questions about liability.

Blue Latitudes does not try to duck these questions. In fact, it gives them visibility on the company’s website. And Hazelwood said she understands people having a gut reaction against the idea.

“It’s hard for folks because you grow up with the concept that you don’t throw anything in the ocean, you don’t pollute, and I’m telling people that those massive structures, those oil platforms, maybe we should keep those in place,” Hazelwood said.

Yes, the oil companies save money in rigs to reefs programs, she said, but about a quarter of those savings, which can be millions of dollars, are passed on to the states for conservation efforts.

“People get upset because it looks like the oil companies are winning,” Hazelwood said. “They are saving a lot of money because they don’t have to remove these platforms. What I hope that people understand is that it’s not just oil companies. We drive cars, we use plastic, we’re part of the reason those offshore oil platforms are there.”

To learn more about the event at The Music Hall Loft visit: themusichall.org/events/rigs-to-reefs.

To learn more about Blue Latitudes visit:rig2reefexploration.org.