"We know that surface use of dispersants decreases the environmental risk to shorelines and organisms at the surface and we know that dispersants break down over weeks rather than remaining for several years as untreated oil might."

VOA: standard.2010.05.18

This type of tag, however, requires a buoy to carry the aerial, and this is attached to the shark by a ten-metre-long line. (The line is needed because the sharks themselves rarely break the surface, and the transmitter cannot signal to the satellite from under water.) Two American biologists, Scott Eckert and Brent Stewart, from the Hubbs-Sea World Research Institute in San Diego, have had some success with satellite tracking.

ECONOMIST: Whale sharks

On the surface, Clara took the break-up pretty well (it was the first time someone had left her).

NEWYORKER: Clara

It is possible that larger seeps at different times and locations might in fact be vigorous enough to break through the ocean surface.

BBC: Methane seeps from Arctic sea-bed