I'm not a sea salt expert but this is what I know. There are different types of sea salt with different uses.
For cooking, the most common ones are Maldon sea salt. Currently, the one in my Kitchen is Morton Lite Salt. Bought mine from Cold Storage. I do not use normal table salt which is supposed to be saltier and less healthy. Everytime I watch cooking shows - Rachel Ray, Jamie Oliver, Nigella Lawson, they use sea salt which they claim is healthier. I don't use a lot as a little goes a long way.
Sea salt comes in various forms - some are normal and some come flavoured with paprika or lemon, etc - for more exotic cooking. Can get those from Jones the Grocer. I think the normal sea salt is good enuf unless u are a gourmet cook and entertains a lot.
There's also another type of sea salt, sometimes these are known as bath salts or epsom salts. These contain minerals and is high in magnesium, which is good to help us keep calm. For a more indulgent experience, you can buy the pricier bath salts from Body Shop, Mt Sapola and rub/exfoliate your skin with it.
What I do is buy Epsom Salt which u can get from Guardian Pharmacy. I can't remember the price now, but I think it was less than $10 per box. If u are using a footbath, sprinkle epsom salt into the footbath that is filled with warm water and soak your feet in it for abt 30mins or when the water turns cool. Very shiok. (how much salt to put in depends on u. I don't measure, just guess-timate. Maybe 5-10 tablespoon? It also depends how big is your footbath or tub that you are using.)
This is supposed to draw toxins out from your body and "refill" your body with good minerals thru the feet.
If you have a long bath, then fill 1/3 - 1/2 box with epsom salts and soak for 30mins or until your skin turns prune-like As we don't have a long bath at home, sometimes, I bring epsom salts overseas to soak in the hotel bath tub when going for holiday.
Personally, not sure if sea salt really helps with water retention, but u can definitely use it for cooking or for relaxing. Just don't use the bath salts salt for cooking.