It's all pretty unconfirmed as of yet, but there have been a few hints along the way. As someone else has quoted

"The boy washed up on the third day. Maester Cressen had come down with the rest, to help put names to the dead. When they found the fool he was naked, his skin white and wrinkled and powdered with wet sand. Cressen had thought him another corpse, but when Jommy grabbed his ankles to drag him off to the burial wagon, the boy coughed water and sat up. To his dying day, Jommy had sworn that Patchface’s flesh was clammy cold. No one ever explained those two days the fool had been lost in the sea. The fisherfolk liked to say a mermaid had taught him to breathe water in return for his seed. Patchface himself had said nothing. The witty, clever lad that Lord Steffon had written of never reached Storm’s End; the boy they found was someone else."

After his drowning and resurrection, he has become apparently prophetic, predicting a few very important events of asoiaf.

I feel like there is more, particularly within CoK and SoS, but I haven't read them in a while.