If you dump the containers over the side, you managed to remove a ship blocking the canal, but now it's blocked by containers.

Right, but you don't need to leave them there. If it's limited depth you could pull them away with barges.

How long do you think it takes to fish a 20 ton container up from the bottom of a canal and load it onto a barge? There are ~10,000 containers.

Barge? Pull it over the edge and worry about it later.

Depending on contents, some might float very well. Or even dissolve away. My dollar store salt-shakers (with salt) came from vietnam.

The top will be the lightest containers, so I’m guessing that’s where your 40 footer of ping pong balls is sitting.

Yes - that's kind of what I had in mind when I first suggested it. When containers fall of ships they often wash ashore on the UK coast. Even a container of motorbikes arrived in Cornwall recently... I'm presuming that only happens because they have some natural bouyancy.

If they don't tear when they hit the water (the metal is pretty thin) they should float shouldn't they? At 77 cubic meters and 30 tonnes their density is low enough, and they're generally watertight aren't they?

Tie heavy duty straps with a small float attached to it before you dump it over the side, then use a tug to pull it away.

I think you're severely overestimating the depth of the canal. I'm too lazy to look up the depth of the specific section where it's stuck, but some sections are just 20 something meters deep.

In other words, just deep enough for ships to come through with little wiggle room. Not as tight as the Panama Canal, but it's not much bigger.

Dumping things over the side, into the canal? That would rapidly block up the canal even worse.

The canal is only 24m deep.... one or two containers would essentially block it for most traffic.

Nature loves you!