Greek engineers were the first to use canal locks, by which they regulated the water flow in the Ancient Suez Canal as early as the 3rd century BC. The Romans under Trajan too secured the entrance to the Red Sea with sluice gates, while they extended the canal south to the height of modern Cairo in order to improve its water inflow. The existence of ancient pound locks to bridge height gaps has been proposed by a number of authors, but in the absence of clear archaeological evidence the question seems to be permanently undecided.
As the older Ptolemaic channel, which was the first to use locks,Trajan's canal linked Mediterranean and Red Sea not directly, but via the Nile. Unlike the Greek channel, though, which branched off the Pelusiac arm, the Roman canal started off the main branch of the Nile at Babylon, 60 km to the south. It joined the Ptolemaic dyke at Belbeis, eventually discharging into the Gulf of Suez at Arsinoe.
Another ambitious project: would have connected Mediterranean Sea with North Sea via Rhone, Saône, Moselle and Rhine; presupposes capacity to construct pound locks though, for which there is as yet no certain evidence; yet, plan finally dropped not due to technological reasons, but political intrigues
Froriep, Siegfried (1986): "Ein Wasserweg in Bithynien. Bemühungen der Römer, Byzantiner und Osmanen", Antike Welt, 2nd Special Edition, pp. 39–50
Grewe, Klaus (2008): "Tunnels and Canals", in: Oleson, John Peter (ed.): The Oxford Handbook of Engineering and Technology in the Classical World, Oxford University Press, pp. 319–336, ISBN978-0-19-518731-1