I still have trouble judging distances [m] any tips?
I used to have trouble with that too. Practice and racing have been what’s helped me the most in gauging how far I am from something. Nearly every race I did in high school was on a buoyed course and the last 250m were always red buoys so comparing where the start of the red buoys were and where the finish line buoys were helped me learn to gauge what 250m looked like on the river when we were practicing. A lot of it is just carefully calculated guesswork though.
I also try and study the river that I’m on to get an idea of how far apart the major landmarks are from each other and then I convert the distance in miles to meters. On the Charles there are a ton of things you can use for landmarks but on your home course it can vary. My coach in high school, who was also a coxswain, taught me that trick and while it’s time consuming, it helped a lot. As I got used to what 50m, 400m, 1000m, etc. felt like it almost became like muscle memory to me so it’s gotten a lot easier to judge distances the more experienced I’ve become.