And I think I will stick with my first answer, If you feel like you're not going to get hurt you should alway try to save the drowning person. The chances of saving a small person are probably greater than a huge man but you should still try.
Another scenario is if the victim is a known sex offender or if the victim is in panic and there a chance they'll pull you down. If the victim is a sex offender you should only save them if you are 100% positive you won't get hurt. I am only saying save the sex offender because life in prison is much worse than ending it. Also if there is a chance that the victim might pull you down then I say still try but be in control and grab them not let them grab you. But still only save someone if you are sure you won't get hurt, losing one person in better than two.
The last part of this is, Should there be laws that punish capable people for NOT helping? I say absolutely not, What determines if someone is capable of saving someone. And thats like saying someone should be punished for not taking the risk of hurting them self. Only the bystander can determine if the can or want to help a drowning person not the law determines that. And saving the person is the right thing but losing one is better than