We went under the first bridge (Atlantic bridge I believe it’s called) pre dawn. 1st Locks were soon after.
for me the highlights were the bridges we cruised under, watching locks open, close, fill empty, etc., and some marveling at the “cut” amount of work involved. Gatun lake is pretty, not much “action” there, lots of other ships to wonder about. We were on the Joy, Feb 2020.