We used the camera in the ocean first time 10 days ago. We did not wash it afterwards. Was working fine till today. The lens wont open. The camera is dead. It does charge. HELP!

Unfortunately you have effectively destroyed your camera. Salt water is up there with fire and crushing as the absolute great unrepairables when it comes to assessing damage. Plenty of owners can and do repeatedly get away with what you failed to do, but you only need to be unlucky once.

Your camera is designed to be waterproof down to 10m (33') for up to one hour, but as with all such devices it must be thoroughly rinsed in fresh water after each exposure to salt water and then left well ventilated to dry. The user manual also clearly states this and gives particular instructions on the way to do so with slight differences depending upon whether the camera has additionally been exposed to sand or soil. A further preventative measure to protect your camera is to have the seals replaced at least annually as recommended by all waterproof camera manufacturers.

If the camera is not rinsed then salt crystals and/or rust form (stainless steel isn't totally immune to rust, and rust can form extremely quickly, especially in salt water). Whether it's salt cystals or rust the effect is the same as they will both tend to shift the waterproof seals slightly and allow water inside. It only takes a tiny drop of saltwater to get inside where, once trapped, it will gradually deposit corrosive and conductive salt traces which effectively destroy the electronics. Once it's in there the only slight chance of a fix is to remove the battery and memory card and then flood the interior with de-ionised water, but this has to be done immediately to have any chance of working. Your camera has now been left too long and so the damage is irreversible and in any case I know of no owner (myself included) who would have dismantled an apparently working camera to flood it with water unless it was known for certain that water had got inside.

Unfortunately your only fix is to replace your camera and to learn from your expensive mistake. I know of no professional repairer who will even attempt a repair to a flooded digital camera; there are simply too many expensive parts which must be replaced and there's too much chance of subsequent ongoing corrosion if even the tiniest mineral deposits remain in the camera.

Sorry I cannot offer you a more positive outcome, but I hope that you now understand why rising is vital and that my advice saves you from repeating the error.

Please take a moment to rate my reply, or if you have further questions regarding my answer then add a comment and I shall respond as soon as I can.