Two Oahu high schools teamed up Friday to combat invasive algae that's suffocating Waikiki's reefs.
Researchers say the fast-growing weed covers nearly 90 percent of the reef outside the Waikiki Natatorium and continues to spread.
You can't see it above water but leather mud weed patches are choking reefs along Waikiki, killing coral, native limu and changing the marine environment completely.
60 students from Kaiser and Roosevelt High Schools pitched in to slow the advancing algae.
"Our philosophy is to protect, preserve and perpetuate our environment, and they really, really want to be here and they're really excited," said Steven Mun-Takata, a Roosevelt High School teacher.
"It's actually sad having to be here today," said Roosevelt student Christina Tauanuu. "It's an honor to help restore the life and make Waikiki beautiful again."
Prized limu that once thrived here is now a rare find.
Researchers believe the brown alien algae came from Maunalua Bay, which is now choking on the invasive weed.
The students not only removed algae, but used GPS technology to map locations where it is concentrated.