While they were under, Rodolphus had pulled the lifesaver in a little, as the eels had tried a few bites and he didn't want the rope to be severed. Once they're visible, however, he slings it their way. It would have been easier and more accurate if he could have used his wand (no, he's never going to stop thinking that in a super grumpy way) but it lands fairly close. Physical exertion is not his strong point, sadly, despite being a fairly big guy, and a little help to haul two sopping wet adults in would probably not be amiss.

"Anyone with a hand free—!" He calls sharply, but he can't actually check, himself. There's another eel approaching and he has to brace himself against the rails so he can use one hand to aim and fire the crossbow.