“Salt Water” that’s exactly a concentration of 0.9% salt, specifically called “Normal Saline”. This is the concentration of all the fluids in our body. There’s no problem injecting fluid that’s this concentration. But if we inject fluid with higher salt concentration, it can cause serious dehydration. If we inject 100% water, it can overwhelm our system, causing burning if injected under the skin, and seizures if infused IV.