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Sailrepair said..I am 57 and sometimes my heart rate looks more like a heart beat trace. Here is my heart rate (grey) with my speed over laid. You can see my heart rate drops at every gybe.

Heart rate is quite variable, but what you are looking at is probably an artifact, associated with the movement you do when jibing, or simply the bouncing over the water (ops, sorry, the beautiful flying over the water, you are on foil). My heart rate monitor, a garmin, shows all possible swings in heart rate when mountain biking. You need a stick on monitor to have any kind of fine grain precision, and even then there is a lot of noise. We used to struggle a lot to analyze heart rate data because of the large variability.
Anyway, to answer the original question. Last year I slalom raced 2015, 56 years old, my heart rate was peaking around 175-180. Now I am on beta-blockers, and it never seems to go above 155-160, most often well below, but I am not in a racing situation.