Diving over another player

[Mattinglyfan]

2nd baseman fielded the ball and over through 1B. Pitcher picked up the ball in Foul territory. Threw the ball to first. My runner was off the bag toward 2nd. When the first baseman caught the ball , my runner tried to get back to first bay diving over the first baseman who had to stretch to catch the throw. The umpire called the runner out. His explaination was only in the Pro's can you dive over a player.