At a colourful temple next to the turquoise sea off Ly Son Island, weather-beaten Vietnamese fishermen offer up their prayers to an unusual god -- "Ca Ong" or Mr Whale.
Before setting sail on a month-long voyage, Nguyen Hoang Loi makes a pilgrimage to the ornately decorated Tan Temple, which houses the remains of two sacred giant whales.
"Praying to the whale will help us if we encounter trouble at sea," the 45-year-old said as he and his crew prepared to depart from Ly Son, an island of 21,500 people off the coast of central Vietnam.
Up and down Vietnam's 3,200 kilometres (2,000 miles) of coastline, fishing communities worship giant whales, which they view as their guardian angels -- a religious phenomenon of a type that experts say is unique to the country.
"If fishermen encounter a sudden storm when fishing and don't know where to shelter, then they pray to Mr Whale to help," Ly Son Island's whale priest Tran Ngo Xuong told AFP.
"The whale will appear beside their boat, helping them through the dangerous moments," said Xuong, a 79-year-old retired fisherman who now acts as a custodian at Tan Temple.
After an elaborate prayer ceremony to appease the whale spirits, Xuong unseals two dimly lit rooms behind Tan Temple's ornate altar piece, where the bones of two giant whales are stored.
The whales -- which weighed between 50 and 70 tons when alive and were both more than 20 metres long -- beached in separate incidents on Ly Son's shores over 100 years ago, Xuong said.
The creatures were so big that hundreds of people would normally have struggled to haul them in, but after many prayers and rituals, just a few dozen islanders managed to drag them ashore with the help of a favourable tide, he said.
Beached whales are given traditional Vietnamese funerals -- they are buried for between five and 10 years, and then their bones are excavated and kept above ground.
Whale oil is separaed off and stored in huge ceramic containers to be used during ritual cleaning of the whale bones on their death anniversary.
Official media frequently report on stories of miraculous escapes by fishermen aided by whales, with Suc Khoe Doi Song, a newspaper under the Ministry of Health, most recently describing fisherman Dang Chau's escape.
Chau's boat was heading back to shore after a long fishing trip when it was caught in a storm. Heavily overloaded with fish, the crew feared they would capsize.
"Then a giant whale came, swimming in front of the boat and blocking the storm so that the crew could sail back to shore," the report said.
"The whale only swam back to sea when the fishermen got to safety. The fishermen were all so surprised, they bowed their heads in prayer to the whale as he swam away," it added.
Unlike in other countries where whales are revered, in Vietnam the practice is based on specific incidents in the past where the giant mammals beached near local fishing communities, according to expert Sandra Lantz.
The Ca Ong religion was, for this reason, "unique" to Vietnam, said Lantz, who authored a 2009 study on whale worship printed in the Swedish Science Press.
The practice of traditional rituals such as whale worship is encouraged by communist authorities, which for decades discouraged all religious activities, before loosening restrictions in 2004.
The majority religion, Buddhist, is now openly practiced, although vocal minority groups of all faiths routinely complain of official discrimination.
Whale worshiping festivals -- which celebrate the cetaceans and ask that the fishermen be blessed with bumper hauls and safe passage across the treacherous seas -- have been given the official seal of approval.
A recent such event in southern Ba Ria Vung Tau was designated one of Vietnam's "top 15 festivals" by authorities.
Ly Son islanders hope the whales could help boost their own tourist arrivals, which currently stand at about 3,000 plus a year.
The authorities plan to reassemble the skeletons and build a new temple to put them on display to attract visitors and make the community less dependent on fishing.