Getting the shocking footage of 'the world's biggest dolphin slaughter' meant enduring grim conditions, and almost getting shipwrecked.
ITV News has obtained footage of dolphins being harpooned hundreds of miles off the coast of Peru and used as bait to hunt sharks.
A video showing dolphins being rescued from shore by beachgoers in Brazil has become an internet sensation.
Animal welfare groups are calling on the International Olympic Committee to stop the planned use of captive dolphins at the Sochi Winter Olympic Games next month.
Endangered Black Sea bottlenose dolphins are due to be used in a display during the Olympic Torch relay in Russia, the Born Free Foundation said.
“Keeping whales and dolphins in captive conditions, where their biological and behavioural needs are compromised, is extremely detrimental to their long-term survival," said Born Free spokesman Daniel Turner.
"The IOC must give full consideration to the welfare of animals in this Olympic Games.”
Japan has defended its dolphin hunts after US ambassador to Japan Caroline Kennedy said she was "deeply concerned" about the practice where local fisherman corral dolphins in a secluded bay before killing many for meat.
"I believe dolphin fishing is one of Japan's traditional fishing industries and is carried out appropriately in accordance to the law," said Japan's cabinet secretary Yoshihide Duga.
"Furthermore, dolphins are not within the management of the International Whaling Commission and it is left to the respective nations to manage this resource."
Taiji Whale Museum staff veterinarian Shinji Sakamoto added: "People are just thinking too emotionally about the dolphins. They want to protect them just because they're cute and clever."
Alison Wood from the Whale and Dolphin Conservation group has condemned the practice of using dolphin meat as shark bait as "wasteful and barbaric".
In an interview with ITV News, she said it was completely unnecessary to butcher the animals in this cruel, inhumane way.
"You can use fish guts, and all sorts of things to bait your hook, you don't need to use a sentient, intelligent animal like a dolphin. It is an awful waste. We are talking about a highly intelligent, social, feeling animal, and to see them hunted like this, is barbaric.
Slaughtering dolphins at sea is a cheaper alternative to other forms of bait for sharks, and the method of killing, harpooning, means that the dolphin can bleed for up to 15 minutes. The blood of the dolphin, then attracts sharks.
The illegal slaughter of dolphins for use as bait to hunt sharks is "an open secret" within fishing communities across Peru, according to marine conservation group Mundo Azul.
Working undercover with the group, British journalist Jim Wickens spent a week on board a shark fishing boat 100km off the coast of Peru, enduring rough seas and a near-death shipwreck incident in order to film the hunt.
For more than a decade scientists and environmentalists have been warning of a mass slaughter of dolphins around Peru.
Hundreds of fishing boats have been accused of killing the animals and using their fatty bodies as bait to catch sharks.
The killings, two or three per hunt, by hundreds of fishing boats around the country, add up each year to make it the biggest illegal slaughter of dolphins in the world, according to environmentalists.
ITV News has obtained footage that shows fishermen harpooning dolphins for bait. It's the first time this secret hunting has been filmed.
Science Editor Lawrence McGinty's report contains images you may find disturbing.
The footage, shot undercover by British journalist Jim Wickens, shows the hunting taking place, hundreds of miles off the coast of Peru.
Davina the dolphin has successfully been released into the sea and is "safe and well", an RNLI spokeswoman has told ITV News.
Once she had been stretchered onto a lifeboat, Davina was transported from the sandbanks of the River Dee to deeper waters at Rhyl Flats.
Watch the Flint and Rhyl RNLI lifeboat volunteers and British Divers Marine Life Rescue take Davina to safety:
The dolphin that got stranded on sandbanks in the River Dee, Chester, is being returned to sea.
Initially named "Dave" by rescuers and then re-named "Davina" after being identified as female, the dolphin was rescued by volunteers from the Royal National Lifeboat Institution this morning.
RNLI lifeboat operations manager Alan Forrester said: "She will probably be much too heavy to lift aboard Rhyl RNLI lifeboat so Rhyl will escort us out to sea.
"The dolphin will be released around the North Rhyl Flats as, if it is set free in any shallow waters, there are fears it will become stranded again."