The big, twin-rotor Army Chinook helicopter — weighing more than 25,000 pounds and longer than a school bus — skimmed low and slow over Waimanalo Bay as a handful of Schofield Barracks soldiers, one after the other, made the 10- to 15-foot leap to the sea from its open tailgate.

After banking around the bay, the helicopter returned to a precise hover, and it became the swimmers’ task to climb up a flailing rope ladder as rotor wash lashed the sea into a sleetlike froth.

“It’s extremely difficult to do,” said a soaked Sgt. 1st Class Steven Mason afterward. “There are a lot of things going on out there in the ocean. You are trying to swim with a full uniform, boots weighing you down. Then the rotor wash from the helicopter is pushing water into your face like the hardest rain hitting you.”

After that, “you are just trying to find a ladder that you can’t really see because the waves are hitting you and then (you are) trying to get up on there,” added Mason, who had performed the task before.

“Helocasting” is not new to the Army, but after a lengthy focus on Iraq and Afghanistan, the 25th Infantry Division continues to get reacquainted with its Pacific roots.

During fighting in the Solomon Islands in World War II, the division earned its “Tropic Lightning” nickname.

“Great power” competition with China, meanwhile, has resulted in the Army working on its maritime skills as it looks to retool and take on a new force projection role in the Pacific. One likely major push would have the Army operate missile and artillery batteries from islands and coastal countries to sink enemy ships at sea.

The ability to conduct helocasting “is an amazing skill for the 25th Infantry that operates within the PACOM (U.S. Indo-Pacific) region and could potentially have to do something like this,” said Mason, 34, who is with the division’s Lightning Academy.

Not many soldiers receive helocast training now, but the Schofield academy, which has the ability to train more than 2,500 soldiers a year in jungle operations, air assault and other skills, plans to expand its helocast program.

Some of the approximately 80 soldiers who took part in two days of helocasting Tuesday and Wednesday off Bellows Air Force Station were with the Lightning Academy and working on validating waterborne skills to pass on to other soldiers.

Reconnaissance soldiers and others with scout platoons also participated.

“What we’re working towards is with the division headquarters to do this twice a year so that units that want to do it can send their soldiers to the course,” said Capt. Andrew Tindall, who commands the Lightning Academy.

Helocasting already is a fairly regular activity around Oahu, with the 25th Combat Aviation Brigade providing the helicopters and in some cases the Marines offering the airborne ride — with the intention of better meshing capabilities across services.

Naval Special Warfare practiced helocasting from a 25th Division CH-47 Chinook helicopter on July 25 in Pearl Harbor. In November, Army Rangers from the 2nd battalion out of Washington state conducted helocasting off Bellows from a 25th Division UH-60 Black Hawk.

On Tuesday, Schofield soldiers were dropped from a Black Hawk that made repeat trips out to Waimanalo Bay. They then had to swim back the approximately 400 yards with a 35-pound ruck sack and rifle.

The following day brought Chinook drops in the morning and Black Hawk trips in the afternoon. For the return to the Bellows staging area during the Black Hawk runs, five soldiers at a time in the water clipped onto a more than 100-foot synthetic rope and then were hauled out of the water and winged back to Bellows to be lowered to the ground.

Hundreds of feet off the ground, the soldiers looked like ants on a string suspended under the chopper.

“It’s overwhelming, but it’s pretty fun,” said Spc. Ikuho Miyazato, 30, after participating in the morning helocast off the Chinook, his first time practicing the skill.

All the soldiers wore masks and swim fins. The week before was spent in a Schofield pool ensuring they could swim adequately.

Sgt. Matt Bates, 24, had done helocasting before, but it was his first trip flying through the air attached to a Special Patrol Insertion/Extraction (SPIE) rope.

“We were probably like 200 feet in the air above the ocean and terrain,” he said. “It’s pretty cool seeing all the people on the beach watching.”

Agile force

The Army’s No. 1 modernization priority is long-range missiles and artillery. The U.S. Army in the Pacific previously said it envisions becoming a more agile force capable of rotating thousands of mainland troops to the region on short notice and setting up temporary outposts in allied nations or on some of the 25,000 islands that surround the South China Sea to fire missiles at adversary ships and bases.

Carl Schuster, a retired Navy captain and adjunct professor at Hawaii Pacific University, said water insertions via helicopter are “a good way to get into a small island without actually landing on top of it.”

Practicing amphibious skills is a good idea in terms of the Army expanding its mission set, he said.

“It basically expands what you can do with what you have without a great deal of additional expense,” Schuster said.