That's into the cooling pool right?

It was the reactor core, but it was shut down for refueling and maintenance at the time. All we know about radiation damage is that their hair was giving off 300 clicks per second (which is an instrument-dependent measurement that can range from "standing in the banana isle" to "take an iodine tablet and get a cancer screening twice a year"), which is probably solvable by shaving off the irradiated hair. Reactors put a lot of effort into making the water at the surface as minimally radioactive as possible (to the point where they are sometimes less radioactive than most water) for measurement purposes. They're probably fine.