Each boat is assigned a number. That number is displayed prominently on the bow of the boat and the back of the man in the bow seat. To tell how any one boat is doing relative to the others, just look at that boat's number and compare it to the numbers of the boats to the bow and the stern in front and behind of that boat, keeping in mind that if crew number 27 is ahead of crews number 26, 25, and 24, it is doing well with respect to the other three.

Naturally, some boats in the race will be faster than others. As the faster ones pass the slower ones, the slower crews are supposed to move to the right. Ulrich said that while there usually aren't many glaring infractions, "in the heat of battle, someone will hog the lane."

The consequences can be disastrous, all of which leads to the next point: where to watch the races. Sweeping curves--either leading into or coming out of narrow-arched bridges--almost guarantee that some gutsy coxswain will make his move, only to lock oars with another crew or be driven into a bridge abutment. Good seats from which to watch all the action can be found anywhere along the river between the Weeks and Eliot Bridges.

Invariably some coxswains fail to take the turn through Weeks footbridge at a sharp enough angle, and their crews head straight for the Cambridge shore. Others make their move on crews in front of the Anderson Bridge, only to discover that three shells cannot fit through the arch at the same time.

In all, the Head is more than just a collection of races. For a day the Charles comes alive, its waters whipped up by hundreds of prying oars, and the crowd takes it all in with the sun cheering each boat as it goes by. The crowd enjoys it; the rowers love it. "I'm so psyched for this race," one rower said when asked what he thought of the day.

It happens all day Sunday. Be there, sports.