Given my double bypass in april - my pace is completely determined by my heart rate monitor - I adjust my pace to keep my heart rate in the target zone.
I learned to row in a Pocock racing shell on Lake Chelan (washington state) when I graduated from college - spent a summer there. The lake is 1.5 miles wide-ish and 55 miles long - it was smooth as glass in the early morning - so nice... I do remember "catching a crab" a few times - the racing shell was extremely narrow and if you catch an oar wrong - you go over into the lake...
My wife and I rowed locally on the willamette river when we first met - she rowed in college... I rowed with her only once in a double - that didn't go well.
jeff