A quick Google shows that the maximum draught advertised on that canal is 1.32m, so that(plus whatever safety margin canals offer in their design) is presumably the minimum depth at any point of the canal. It would likely have areas which are somewhat deeper.

It also consists of a series of locks which increase elevation by approximately 2.5m each, so any one of those if full would be too deep to stand up in.

There are a lot fewer staff around than TV would have you believe. You would need basically 1-on-1 supervision until the drug wore off, which is very resource intensive compared to a one-time intervention.

I mean, is that not what they all did?

Put a thermometer in plain view and tape your phone number to the window as a backup in case someone is unable to see the thermometer, or your AC has malfunctioned and there is an actual issue.