You have tanned due to sun exposure. It has nothing to do with the salt content in the water. Tanning is a protective mechanism to prevent your skin from developing cancer. People who tan easily do not develop skin cancer easily and vice versa. To prevent a tan you will either need to avoid sun exposure or use a sunscreen every 2 hours when you are outdoors. To remove a tan you could use detanning creams prescribed by a dermatologist. Detanning makes your skin very sensitive to sunlight and you will need strict sun protection when using them. Also procedures like chemical peels can be done to remove a tan. Visit a dermatologist near you for more details. Warm regards. Dr. Rajdeep Mysore. Chirag Hospital Bangalore