Salt water itself is not bad for your skin. It may be however, that the constant exposure to the water, the sun, and the sand is irritating your skin somewhat mechanically. This is especially the case if you have a personal history of sensitive skin or eczema
If so, you should be able to treat this easily by keeping the skin well moisturized. After swimming in the ocean, take a quick shower to get any residual salt and sand off. Then, apply a good, thick skin moisturizer all over the affected areas. If you do this regularly, I think you will see things clear up.
There is one interesting condition that is worth mentioning. This is called 'sea bather's eruption' and it is an intensely itching rash that develops in some people after swimming in the ocean, particularly near the Gulf Stream and in tropical areas. This itching rash is a reaction to tiny microscopic jellyfish larvae swimming in the ocean. It can be managed by prompt showering after swimming and also by applying anti itch over the counter creams to particularly inflamed areas.
Talk to your doctor
for more advice if you are still having problems after trying these suggestions.