[kinofcain]

That's certainly a good data point in the 'against' column, but it really only indicates that any current, if present, isn't likely to be caused by the normal circulation of water from filtration systems or similar. There are a number of other things that could possibly be causing a current.

For instance the current could be caused by the interaction between the pool and the motion of the swimmers in the pool. It could be caused by the overflow wave from 8 people entering the pool. It could be caused by uneven gutter heights leading to the pool draining at a faster rate on one side/corner. It could be a combination of all of these things, none of which would show up in a static test like the one they demonstrated.

The fact that this has happened at some races and not others, and the ones it looks like it has happened at are Myrtha pools, is interesting in itself.