Are sharks colourblind?

http://news.bbc.co.uk/earth/hi/earth_news/newsid_9365000/9365750.stm

Extract:

If sharks' retinas cannot distinguish between different colours of light, as this research suggests, they may be totally colour-blind.

Dr Hart explained that, because sharks live underwater and many are most active at dawn and dusk, they are operating in relatively dim light.

"Rods are what humans use to see at night," he said.

"But some sharks are active at all times of the day and they have more cones and fewer rods than the nocturnal or deeper diving species. Why they are apparently not interested in colour is a mystery and one we hope to find out through further research."

It seems clear from these findings that if sharks are "attracted" to an object in the water, this is probably because of its contrast against the surrounding water, rather than it's colour.

"Bright yellow is supposed to be attractive to some sharks, presumably because it appears to the sharks as a very bright target against the water," said Dr Hart.

"So perhaps it is best to avoid those fluoro-yellow shorts next time you are in the surf."