What each boat skipper does before the start of the race (well its actually a time trial) is nominate the exact time it will take him to get from one point to the next, over the complete course lay out.
The marker boats click them off as they latch through each time trap marker. Can be up to six of these over a course, and may run two three laps. Disqualification can be from speeding up or slowing down approaching a time trap or missing a time trap completely.
Marker boats are usually sailing crew from Summer races. Winter crew run rescue for sailing during Summer.
Very serious stuff, stink boat time trials
