New Tools Help Divers Survey Reefs in Papahānaumokuākea

September 12, 2025

Picture yourself as a scientific diver on a team whose job it is to cover one of the largest marine protected areas in the world in just under two weeks. One might ask, how is that possible? On Aug. 23, the NOAA ship Oscar Elton Sette departed Honolulu with a crew from Papahānaumokuāea National Marine Sanctuary, who set out to do the seemingly impossible.

scuba divers hold onto torpedo-shaped devices with propellers as they glide above the reef making observations — NOAA divers Brian Hauk and Jason Leonard on closed circuit rebreathers use diver propulsion vehicles to survey for nuisance algae at Manawai. Photo: Nick Zachar/NOAA

From the waterproof paper invented for fish surveys, to today's diver propulsion vehicles, technology has long advanced scientific diving. On this mission, researchers are using diver propulsion vehicles, or underwater scooters, for the first time to document nuisance Chondria tumulosa algae across the northern three atolls—Kuaihelani (Midway), Hōlanikū (Kure), and Manawai (Pearl and Hermes).

Technical Assistance and Training

Dr. Chelsie Counsell, a Cooperative Institute for Marine and Atmospheric Research supervisor working for Papahānaumokuākea National Marine Sanctuary, developed a new survey method compatible with closed circuit rebreathers and diver propulsion vehicles. Office of National Marine Sanctuaries team members, Jason Leonard and Brian Hauk, tested the approach and refined it for accuracy and reliability.

Traditional scuba limits dive time, because each exhale depletes a diver's air supply Closed circuit rebreather systems recycle exhaled air by removing carbon dioxide, extending underwater time and efficiency.

Using closed circuit rebreathers with diver propulsion vehicles allows the NOAA divers to survey continuous stretches of reef for about three hours, covering more ground safely on limited field days.

a scuba diver uses tools underwater while wearing a complex set of hoses and spare tanks on a rebreather setup — NOAA diver Jason Leonard using a closed circuit rebreather system while recovering an acoustic trap in Lalo. Photo: Nick Zachar/NOAA

Why it Matters

Papahānaumokuākea's remote location and narrow weather windows make efficiency critical. Technology like diver propulsion vehicles helps divers quickly survey reefs to detect changes such as crown-of-thorns starfish outbreaks, track herbivorous fish populations, and monitor nuisance algae.

Long-term monitoring reveals how ecosystems respond to disturbances and ocean changes, supporting NOAA's mission to safeguard sanctuary resources, bolster resilience, and guide management decisions with data.

a scuba diver writes on waterproof paper underwater while surrounded by a school of fish. The diver propulsion device is inactive and clipped off to their side while they work. — NOAA diver Brian Hauk practices conducting surveys while diving on a rebreather system and using a diver propulsion device. Photo: Jason Leonard/NOAA

Stay Tuned

The team will return to Honolulu next week with a wealth of new data to process and share. Stay connected with NOAA Sanctuaries and Papahānaumokuākea National Marine Sanctuary on social media for updates on the mission, research highlights, and team insights.

Jennifer Crawford is the Pacific Islands Region communications coordinator for NOAA's Office of National Marine Sanctuaries

Rachel Plunkett is the content manager and senior writer/editor for NOAA's Office of National Marine Sanctuaries