[video=youtube;J5iPbihuzPc]http://www.youtube.com/watch?v=J5iPbihuzPc&list=TLtev2agKCtxjaUYPxm0yyfsz0hZizAnuJ[/video]
Per the article: "The balls form when chunks break off the massive ice sheets that coat parts of the lake in the winter...They gain their shape as waves in the lake ceaselessly toss them about, slowly rolling them into spheres." Nothing you'd want to paddle out through.