If I were to do it though, I would invest in some water filters which are fairly cheap and can remove a lot of things that you wouldn't want to be drinking.
(Though there might be some obscure edge case, and if you're about to die of dehydration that a little bit of seawater will buy you a minuscule amount of more time? doubt it)
If you're about to die of dehydration - from sweating - and have not been rehydrating you're already also hypernatremic (too salty) as well so I sort of doubt it would help. Sweat is less salty than your blood so it increases salt concentration.
Every account of people stranded at sea that survived points to them getting hydrated through rainwater, or fish/turtle blood that they hunted, or even dirty non salty water enemas.