To answer my own question (or rather get an answer from one of the Training Division riders):
"It was a drop into water - you had an option you could the lower side but the edge was hard to see or the bigger side with a little log on top. I chose the bigger side because I wanted the defined edge. It was simple looking - the only reason I can think for the issues is you come into the field and go up a hill so the horses don't see the water right away? there was also a log on the base of the water side - it was really designed to jump up - that caused them to jump out a little instead of drop down. My horse leaped and unseated me goinig into the water - I came really close to falling off in it & jumped 7 w/o stirrups."
Brock n. (Anglo-Saxon) badger as in Brockenhurst, Brocklebank etc www.area35.us