ADH enhances water reabsorption. Aldosterone increases the kidneys' salt retention. Answers will vary. Survival of the fittest. High salt concentration in sea water would cause water to leave your cells thus increasing dehydration.
Dehydration can be deadly.
Renin boosts aldosterone levels. Aldosterone increases salt retention. Increased salt retention can cause increased blood pressure. Protein does not filter out, so it shouldn't be in the urine. Not enough push to keep substances moving properly.