Washing it thoroughly in fresh water is better than doing nothing.
I have "saved" a cellphone that was dropped in a bucket of concentrated water/chlorine solution and a radio pager that was dropped in salt water - in each case by very very very thorough washing in fresh cold water with no cleaning agents and long slow drying. A lens MAY respond to the same treatment BUT optical surfaces may be left with a film that affects operation and lubrication may be affected. Some parts may be directly damaged by water but usually these would be auxilliary parts (tape etc). Power must be removed asap if there is electrical connection - voltage + salt water causes rapid corrosion and a powered electronics board in contact with salt water MAY die in seconds to minutes. Some may not.
Best approach is professional attention immediately.
If you take a lens off a camera (removes power) and fresh water rinse it until all salt is gone IMMEDIATELY after it gets salt water contaminated then you MAY save it. Leave it a day and it is probably dead without careful work. Longer again is worse.
A lens repair expert MAY agree to work on the lens but some will decline to do so because they cannot guarantee the result. (Ask me how I know :-) ).
If you cannot afford to get it repaired you MAY be able to get it working by:
(1) Dismantling the outer but not touching the mains lens assembly and washing it very thoroughly in clean cold water. Do not use detergent etc. For some lenses you can find detailed disassembly instructions on the internet. If you dismantle the core of lens elements that do not usually move relative to each other you will about 99.99% certainly need professional alignment assistance to restore functionality. It MAY help to lubricate gear drive track and cogs etc with a recommended lubricant if you can find instructions and the right lubricant BUT cold fresh water has a reasonable chance of not displacing at least some lubricant.
If that is too challenging, you could try...
(2) Washing it many many many times in clean water so water enters it well on each occasion and then drains out and then leaving it in a warm dry place for as long as it takes to dry totally - weeks probably MAY work.
Overall the chance of long term success is not good.
But, just drying out the salt water is even more likely to be fatal.
What do I know: I'm a professional electrical engineer and inveterate tinkerer with things electomechanical. I have experience with corrosion protection and have cleaned salt water damaged lenses and other things with variable success. Caveat Emptor / All care no responsibility / YMMV.