I'm afraid this is where your "happen to think" rather falls over... ☹️ Nobody -- including me -- is saying that the Bernoulli effect doesn't happen on canals, including being drawn towards by-washes (as you point out) and bottom gates when just outside them (as Nick pointed out) -- though in the by-wash case it's still more likely to be water going under the boat and bouncing off the opposite bank that pulls the boat towards it, Bernoulli would just pull the boat downwards. However that doesn't mean that it's the dominant effect going on in locks, especially because the water flow is not continuous and static or indeed enclosed -- though that's not what Bernoulli actually says, it says that the total energy including dynamic and static head is constant. But as usually interpreted, it's taken to mean that when you speed up water flow its pressure drops. So let's look at what happens when you're on a typical boat in a lock -- and let's make the boat somewhat shorter than the lock and sitting next to the bottom gate (the usual case). From actual observation, when you open the paddles and water starts to flow in and fill the lock, the first thing that happens as the water travels down the lock is the bows of the boat rise and it gets pushed towards the bottom gate as water flows under the bows and lifts them. If this was Bernoulli (pressure drop with water flow) the bows would drop and the boat would move forward -- but it doesn't, at least not just yet. The next thing is that this incoming surge of water passes under the boat and hits the bottom gates and some bounces back (because the energy involved in reversing the direction raises the level), and the stern of the boat lifts by a few inches -- you can clearly see this by watching the cabin rail line against the brickwork lines. Then the boat moves strongly forwards towards the top gate, sometimes so much that going full astern can't stop it -- this can't be driven by the Bernoulli effect because there's no strong high-speed water flow under the boat, it's quite slow. Then the water eventually settles to level, and the boat usually drifts gently back towards the bottom gate as the lock fills with water from the top paddles. All this is mostly driven by changes in water level and gradient (and pressure under the boat) as the lock fills, not the dynamic flow of water (Bernoulli) as such because the water velocities under the boat are too low -- 1m/s would give a pressure drop of 0.07psi, a lot less than that resulting from what you see from the changes in water level. There's also the problem that any water flow under the boat tends to be relatively uniform along the length, which would make the boat sink as a whole not tilt/accelerate. If the boat bows are right over the paddle flow then the water speed of the jet from the paddle is a lot higher but it's mostly lateral and only under a small area of the boat, so has less effect than you might think. So it's not that the Bernoulli effect doesn't happen, it's that given the level changes and water velocities inside a lock it has a smaller effect than the water level changes do. At least, that's what hydrodynamics and the numbers say, as opposed to prayer or opinion or "because I say so"... 🙂
