You know, humans cannot drink sea water, they would die. If drinking salt water were the best water for us and the animals, I am sure nature would have provided for it. Take for example, human breast milk. We know how important the hormone "vitamin" D is for healthy growth of bones in babies, yet nature has neglected putting it into human breast milk. As we know, children were meant to be outside as it is still practice in most developing countries (you don't see them locked up in their dark huts). Since these babies make their own vitamin D in response to regular exposure to direct or indirect sunlight, they develop strong bones and healthy teeth. Why put it in the milk when there is a much more efficient way of making it than digesting and absorbing it through food?
Likewise, although we need salt to live, nature didn't put it in the water. Our body makes a certain amount of sodium chloride from hydrochloric acid and sodium bicarbonate (both produced in the body). Whatever else it needs it will get through natural foods and eating salt. For a temporary rehydration process I do recommend to add a pinch of salt to the drinking water, but not otherwise. I just trust that nature didn't make mistake by giving us sweet-tasting water instead of salty-tasting water. Many times we think we know a new trick because it sounds so logical, just to find out that it wasn't such a good idea after all. If you feel drawn to trying it out, go for it. The best learning occurs from trying things out. I did it myself for a while but didn't notice a difference, except for some dryness in the throat area.
I personally never used senna. It is a purgative and many purgatives can be habit-forming in that after discontinuation, constipation may recur. Addictive is perhaps not the correct word to describe it. It should not be used when there is intestinal inflammation or hemorrhoids. It can be very useful for women after pregnancy, if combined with other herbs that prevent nausea, like ginger. If the urine turns red, it is not because there is blood in the urine, but because senna has strong colorants.