What is the name of that book?

It's like Malcolm's Millions or something like that.. I read it when I was little. It was about this boy who goes through a black hole in the basement of his own house, and sees these stingray type creatures. He could stay there for about 30 seconds, but when he goes back home, it would be about 6 hours. Anyway, it was my favorite book back in the day and I would really love to read it again, but I forgot the name of it.