Sea spray is horrible. Try lens cleaner, from opticians, but if it's bad, I would wash in warm soapy water. Dry the surfaces with kitchen roll and then put in the airing cupboard overnight, then brush off any particles and finish off with a microfibre cloth.
Some filter coatings can be permanently marked by dried on water, so don't be surprised if there are some small residual signs left. It won't do any harm but water should always be wiped off immediately.