An annual indoor rowing challenge that Concept 2 sponsors is to do 21,000 meters on the 21st of June which is the longest day of the year. They suggest adding 97 meters to the 21K, which brings the distance to a half marathon, which is a little over 13 miles.
So I joined an online HM today and did the half marathon slowly with only one break for a call of nature.
Happy half marathon rowing to you.