Some lenses can be worn while swimming in the ocean, however, there is a danger that the lenses will be lost. Also keep in mind that the water you’re swimming in may contaminate your contact lenses with harmful bacteria. You should consult your optometrist about swimming in the ocean with the lens type you are wearing.

[source: http://www.crcert.org/research/do_you_wear.htm ]

"yes" As a contact lens wearer and an avid ocean guy (bodyboarding, surfing, swimming, frolicking, etc...) I'm in the ocean with my lens & have done so for a number of years. I've tried wearing it under goggles but i'm uncomfortable with the goggles. I've lost a few lenses though albeit a rare event (usually one at a time but there was an incident where I actually lost both! Lucky for me, I happen to have my glasses in my car that day). You usually lose a lens when the water gets in between the lens & your eyes, which then pushes your lens off.

I agree with kanjalid (and be sure to check the link that she provided) with bacteria and the proper care of the lens after being out in the ocean.

For underwater activities, I would wear a divers mask with my lens on. If you really want to do it right or if you're going to do it often (underwater activities) then I would purchase a divers mask with prescriptive lens (yes these are available). I also would advise taking periodic breaks to re-hydrate your lens with the proper lubricant eye drops.

There is bacteria and parasites in ocean water. The contact can act as a meduim for growth. Their are cases where people have gone blind from this scenario. Look up pseudomonis sometime. This parasite can eat and infest the cornea of the eye. Untreated, this can lead to blindness. If you wear your contacts in untreated water, throw them away afterwards and put a new clean pair in. It's not worth the risk.

no it is not ok to wear contacts in any type of water cos if water gets inbetween your contacts and eye and stays there for more than 2 hours you can become blind