AN explorer's life is all about firsts. In a career with records and accolades following one another like pearls on a string, Sylvia Earle may have reached another first marine scientist to make an important shark discovery in the middle of an environmental disaster.

On a research mission to the Gulf of Mexico recently, in waters 70 miles off the coast of Louisiana but still clear of the oil and gas spewing from BP's runaway well, Earle and scientist Eric Hoffmayer were surrounded by dozens of supersized whale sharks.

Earle, explorer in residence at National Geographic, believes it may have been the largest such congregation ever observed by scientists in the northern Gulf of Mexico. “It was an ocean full of whale sharks. I can't even begin to count the fins,” she said. “We almost had them bumping up against the boat.”

The animals are the giant living hoovers of the sea. Forty feet long, they skim along the surface of the water, swallowing up the nutrient-rich sargassum mats of seaweed. They are also officially classed as a “vulnerable species”. With oil gushing in the Gulf, their feeding habits, indiscriminately gobbling at the ocean surface, put them at an even higher risk. “Whale sharks in the Gulf may be on death row because they skim right at the surface where oil accumulates,” said Earle.

The people who know the oceans inside out and from the bottom up are a small, self-selecting group, and Earle, a legendary diver, explorer, scientist and author is a charter member. Now 74 — and still diving — she has logged more than 6,000 miles underwater. In the Gulf of Mexico, she has dived to 2,000 feet.

So for Earle and her fellow ocean scientists the spill is deeply personal. At a recent conference in which Earle also spoke, a number of scientists were choking back tears as they described what was happening to the creatures that live in the Gulf. The ocean floor is not terra incognita for Earle. She literally calls it home and over the years profile writers have remarked how much more comfortable she looks, dripping wet and in a wet suit, than on land.

Diving, she said, is like plunging into “a galaxy of flash and sparkle”. The ocean floor is like a big underwater city.

“The bottom of the ocean is not just rocks and mud, or mud and sands, although that is an image a lot of people have,” she said. “On a sea floor that looks like a sandy mud bottom, that at first glance might appear to be sand and mud, when you look closely and sit there as I do for a while and just wait, all sorts of creatures show themselves, with little heads popping out of the sand. It is a metropolis.”

And yet, Earle can only speculate at the ruin done so far and the damage still to come. The poisoned waters in the Gulf could well swirl around Florida, and up the Atlantic coast. She notes that jellyfish caught up in the Gulf stream travel 99 miles a day.

“The magnitude of this tragedy has yet to sink in. It is taking time to realise just how dire this is and how long term it is likely to be,” she said.

Much can only be guessed at because scientists and governments are pitifully behind the big oil companies in terms of technology. “We should know. We should have invested in the technology and the research to know what is happening before, as well as to track it in real time. Now it is maddening to feel the urgency and to feel so helpless.”

Like other ocean scientists, she is highly critical of BP for withholding information about the spill.

The footage made public so far of oil and gas billowing from the site of the ruptured well is as useful to science as wallpaper, she said. “It is a little like the yule log image you start seeing around Christmas. It's mesmerising but it doesn't really tell you what is happening,” she said.

— The Guardian, London