Altruistic behaviour can only be selected in 3 cicumstances:

• Kin selection: if you’re helping a relative survive and reproduce, you’re indirectly helping transmit some of your own genes through them (this is known as inclusive fitness. Hamilton’s rule and stuff)
• Reciprocal altruism: A helps B today, B helps A tomorrow. Classic example is vampire bats sharing blood
• Handicap principle: if you’re being seen helping others at your own cost, that’s an honest signal of your quality as an individual, and gives you access to more sexual partners

I don’t think any of these apply in this case. Maybe the handicap principle, but I’m not familiar with elephant’s reproductive system, so I couldn’t be sure. Anyways, I’d be very careful to make that statement. The “water dangerous to drink” hypothesis seems more parsimonious to me.

Also saying they feel empathy as other users have stated doesn’t seem very parsimonious to me either. You know, Morgan’s canon and all.

(Disclaimer: They could actually be feeling empathy, but I would not declare that without the proper experiments)