Traditional Thames pleasure punts were not introduced to Cambridge until about 1902–1904, but they rapidly became the most popular craft on the river, and today there are probably more punts on the Cam than on any other river in England. This is partly because the river is shallow and gravelly (at least along the The Backs) which makes it ideal for punting, but mainly because the Cam goes through the heart of Cambridge and passes close to many very attractive old college buildings. However, the popularity of punting beside the old colleges in Cambridge produces significant congestion on this relatively narrow stretch of the river during the peak tourist season, leading to frequent collisions between inexperienced punters.

(Source Wikipedia)