Navy divers today are expected to assess the recovery of a Marine Corps amphibious vehicle that sank Monday night off Bellows Beach.

All crew members were evacuated safely by another assault amphibious vehicle, or AAV, participating in the training exercise, Marine Corps Base Hawaii said.

The 28-ton, tank-like vehicle sank in 20 to 30 feet of water during a platoon exercise off Marine Corps Training Area Bellows, officials said.

The corps said the AAV was hit by a swell more than half a mile offshore. The wave caused the vehicle to strike a reef, and it began taking on water, officials said.

The troop carrier lost power while attempting to reach the shore and sank about 6:30 p.m. about 500 feet from shore, officials said.

The incident is under investigation.

Navy divers from Mobile Diving and Salvage Unit 1 are expected to dive to the sunken vehicle today to assess its recovery.

Officials said the divers may use float bags to raise it.

The Coast Guard said it was monitoring the situation. Coast Guard Petty Officer 3rd Class Michael De Nyse said the AAV has 170 gallons of diesel fuel, but that there was no indication of leakage.

Marine officials said seven of the armored vehicles with the Combat Assault Company AAV Platoon were conducting scheduled AAV water operations Monday.

On real-world missions, the AAVs would drive out the back loading ramp of a ship, but for Monday's exercise, the vehicles drove out from the beach and back.

Sgt. Macario Mora, a Marine spokesman at Kane'ohe Bay, said the base has 12 AAVs, including the one that sank.

The troop carriers, which have been widely used in Iraq by other Marine units but have not deployed from Hawai'i, can carry up to 25 Marines in addition to a crew of three.

Mora said he wasn't aware of any other Hawai'i-based AAVs sinking in the past.

The last incident involving one of the vehicles was on March 15, 2006, when there was a malfunction, but the AAV made it to shore, he said.

The normally very buoyant AAVs, which have been in the Marine inventory since the 1970s, have been known to sink, including off Okinawa in 2003 and 2005.

The Marines had planned on replacing the AAVs with speedier Expeditionary Fighting Vehicles, but the replacement vehicles' future is in question.