Easily compensated?

https://eodg.atm.ox.ac.uk/user/dudhia/rowing/physics/weight.html

Check section 8.

> So if a 85 kg oarsman pulls a 5 km erg in 19 minutes (=1140s), and a 70 kg oarsman takes 19.5 minutes (=1170s), their equivalent 'boat speeds', normalised for a 75 kg oarsman, would be:

> (8.8) (85kg): TB = 1140 / ( (90/100)0.167 ) = 1160s = 19m 20s > (8.9) (70kg): TB = 1170 / ( (90/85)0.167 ) = 1159s = 19m 19s

> i.e. a bit of a nightmare for the person who has to select between the two. (Using the 0.222 power would give times 1167s and 1155s respectively, so the lighter rower would win).

Now this is using accepted formulas for estimating rower performance on water based on an erg (indoor rower). So it's not perfect, but it's a great example of why not being bigger didn't mean faster. Remember drag is constant for all movement including coasting.

So in this example the 15kg heavier person would be about the same speed as the 70kg person. You can't assume that the extra weight will always be just muscle. Fat, bones, etc count as well. You are unlikely to increase just muscle (at best you will have a body fat percentage of around 5-8% for an elite athlete). So any increase in weight will carry dead weight as well.

Physics dictates that you need to increase displacement in order to float a heavier weight on water. The more water you displace the more water will be in your way when you try to move. Drag is drag and it affects you. People can only gain so much strength improvements with weight.