Since the ocean has iodine in it, why doesn't sea salt?

It does but only trace amounts. Table salt in contrast under goes a process to add iodine. This has been going since the 20s to help prevent certain diseases. Sea salt is a more natural product and as such doesn’t contain other things added to table salt like aluminum compounds that prevent caking.

Has anyone used this as a bath soak ?

I often add 1 cup coarse to my bath, especially when I'm in the US and I know the water of my bath has Fluoride. It's great!!!

What is the mineral content?

Celtic Sea Salt contains essential electrolytes like sodium, potassium, and magnesium, which are vital for maintaining proper fluid balance, nerve function, and muscle contractions. It contains a variety of important trace minerals, such as magnesium, potassium, selenium, copper, zinc, iron and manganese. Celtic salt has a much higher trace mineral content (17.5%) than Himalayan salt (4.1%). Many naturalists recommend Celtic salt.