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.
The data they collect pinpoints trouble spots targeted for future clean-ups.
Other students count native sea urchins. They are natural predators that help control the marine environment by gobbling up the algae.
Kaiser teacher Michelle Kapana-Baird says some students are interested in marine science; others simply care about Hawaii's waters.
"Some are just -- they love the ocean so anything they can do to help and protect it, they're all good with that," said Kapana-Baird.
Coral researchers hope today's event makes students more aware of the serious problems caused by invasive species.
"When they go to the ocean and they see an alien, pick it up, take it home, plant it in your garden because it works really well with compost," said Pam Fujii of the Hawaii Coral Reef Initiative.
Kaiser and Roosevelt students will continue to clean invasive algae around Oahu through the school year.