The people that dive with whales that could eat them alive by David Cox, BBC

Sperm whales are the biggest living things with teeth, and they seem to “talk” to each other. To decipher their messages, scientists are free-diving with them.
A decade ago, Fabrice Schnöller was an engineer working on systems for tracking sharks. Then, in 2007, he went on a sailing trip to the island of Mauritius, where something happened that would change the course of his life.
As his boat approached the coast, giant towers of steam began exploding out of the water. One by one the columns closed in, until they surrounded the whole boat. Curious as to the source of this strange ocean phenomenon, Schnöller grabbed his snorkling equipment and a camera, and jumped in.
Diving down beneath the ship, Schnöller’s ears were bombarded by what sounded like underwater explosions, growing louder the deeper he went. At first he feared the boat had suffered a mechanical failure. But as he circled around, he began to sense that he was not alone.