Steve Trewhella/YouTube

Wildlife photographer Steve Trewhella was on a tourist boat in the San Ignacio Lagoon in Baja, California when he spotted a couple of female gray whales in the water near their boat.

The whales — which can reach 45 feet long and weigh up to 30 tons — could easily flip the boat over, or even crush it. 

And after a few minutes of monitoring the tourists from a distance, the whales began to approach.

Surprisingly, as one of the large females made its way towards the boat's edge, Trewhella and the other tourists on board didn't panic. Instead, they reached over and began to pet their curious guest. Amazingly, the huge whale merely floated on her side on the water's surface, allowing the tourists to pet her. It almost seemed like she was savoring the attention.

This type of interaction doesn't happen everywhere.

In fact, Trewhella, 52, told The Daily Mail that the lagoon is "believed to be the only location in the world these gray whales interact with human beings on this level."

Watch the stunning interaction captured by Trewhella below:

 The San Ignacio Lagoon, a UNESCO World Heritage Site that is protected by the Mexican government, is a critical stop on the whales' yearly journey from their feeding grounds around Alaska in the Bearing Sea, Beaufort Sea and Chukchi sea, where they mate and bear their young. This annual journey is a mammoth 12,400 miles round trip.

Here's a GIF of a whale and her calf approaching curious tourists:

Protection of this lagoon is vital since gray whales are currently found only in the North Pacific. There used to be a population of whales in the Atlantic Ocean, but it was completely wiped out by whalers by the mid-1700s. Of the populations in the North Pacific, these whales belong to the Eastern North Pacific stock that feed around Alaska, and migrate down the west coast of America to breed in Mexico. The Western North Pacific stock feeds near the Sakhalin Islands on the east coast of  Russia during the summer, and are believed to migrate to the South China Sea in the winter.

Here's a look at their international route:

NOAA

In the 1900s, both the Eastern and Western North Pacific populations of gray whales were classified as endangered due to heavy commercial whaling. Nearly five decades after commercial whaling was banned in 1947 by the International Whaling Commission, one group of them — the Eastern North Pacific Stock — was removed from the endangered list. 

However, the Western North Pacific stock has not had the same luck. 

Watch a grey whale breach near a tourist boat below:

Countries surrounding the Western North Pacific Stock continued to practice whaling until at least 1966, prohibiting them from signing on to the ban. According to a joint Russia-US research program, the population size of this stock was just approximately 130 animals in 2013. Experts suggest their ranks are growing, but very slowly.

This small population is on the endangered list even though commercial whaling is banned. The main hazards to the stock are still human activities — entanglement in fishing gear and disturbance from offshore oil and gas activities. 

It is believed that the oceans once supported a population of 100,000 gray whales. Only a fifth of that number of gray whales still remain. While many like Trewhella get the chance to fearlessly interact in close proximity with these mammals, and be amazed, on the eastern edge of the Pacific Ocean, those across the water are not so lucky.