My dad used to take me to see the start of the boat race most years. It was a big event back then. Dad and I supported Oxford and mum Cambridge. I don't know if it applies these days, there were quite large crowds on the river bank. The days when south west London was a lovely place to live.
Just remember that we used to wear dark or light blue ribbon rosettes to school the week before.
To warn an errant crew that they are (e.g.) taking their opponents ground. It's a bit strange because the person steering the boat is the cox and he has his back to the umpire. More useful for races involving coxless boats.
Watching the boat race on TV was a big deal when I was growing up. So sad that we have kowtowed to those with views like 10CS, slowly all our traditions are being diminished by the low life.