I know this is a bit hashed and dead already, but I think you've misunderstood libertarianism, particularly the Objectivist branch you seem to be implicating and sneering here.
A libertarian lifeguard, particularly an Objectivist Libertarian, would have gone into the lifeguard job fully conscious of his own personal value. A libertarian lifeguard would be a well paid and first-class professional because entering into a contract to risk one's life would require adequate compensation. No ill-trained pimple faced teenagers at a libertarian pool!
The same would follow for firefighters and police where they are needed.
But your beautiful altruistic romanticizing of lifeguards, firefighters, police etc, is overcooked as well. They are all trained not to risk their lives, if they can't engage safely. It is drilled into their heads that there is no need making a bad situation worse, by adding another victim (themselves) to the carnage, by racing into a dangerous situation. They are taught to assess and rationally attack the problem in the safest, least risky manner possible; they have many tools designed to limit risk in their jobs. Think of the red flotation devices and hooks hanging on the walls of the pool. Instructions are explicitly given to NOT commit self-sacrifice (suicide) to save another. They are instead contracted and paid to do the best they can, in bad situations, without getting themselves killed in the process. How self-sacrificing, altruistic is that kind of training?
No. Instead what lifeguards and others do for us is performed in a common sense, libertarian, manner already. Would you ask them to perform their jobs any other way? To throw themselves into the pool of drowning victims at any cost, even if it's their own life, for a $7/hr paycheck, to save perfect strangers? Why do you hate lifeguard's right to their own life above the lives of others?
Libertarians don't understand your self-sacrifice at any price, mentality. Not without a proper contract that appreciates the risks of the lifeguard, and especially not for strangers.