For the Suez Canal a huge bomb is just going to make it bigger and easier to navigate in one spot.
Blow up the locks for the Panama Canal and you have some seriously inconvenienced shipping companies.
But even in both cases the result is that they have to take the long way around. It makes the shipping slower and more expensive, but it was a tiny fraction of your costs to begin with so most companies survive just fine.
For the Suez Canal a huge bomb is just going to make it bigger and easier to navigate in one spot.
A huge bomb to one side of the canal would displace rock and mud in to the channel and make it shallower. That would be enough to close it to large ships until it could be dredged again.
Although, if terrorists really wanted to wreak havoc in the canal they could scuttle a large ship while it's sailing in it. That would necessitate dismantling and removing the entire thing.
> In October 1967, the officers and crews of all fourteen ships met on the Melampus to found the "Great Bitter Lake Association" which provided mutual support. Crew members continued to regularly meet on board their ships, organized social events, founded a yachting club and held the "Bitter Lake Olympic Games" to complement the 1968 Summer Olympics in Mexico City. Life boat races were arranged and soccer games were played on the largest ship, the MS Port Invercargill, while church services were held on the West German motorship Nordwind and movies were shown on the Bulgarian freighter Vasil Levsky.[2] The Swedish Killara had a pool.[3]
> In time, it was possible to reduce the number of crew members on board the ships, and in 1969 the ships were gathered into several groups to further reduce the number of crew necessary for their upkeep. Those crew that were left to maintain the vessels were rotated every three months. In 1972, the last crew members of the German ships were finally sent home, with the maintenance of the ships left to a Norwegian company.
I remember back in the early 90s attending a CEBIT trade show (at the time perhaps the largest computing show in the world -- the show floors covered acres) and being astonished to see that the Bundespost delivered mail, including the usual trade show flyers, to each display booth. Yes, uniformed postal workers wheeling the usual delivery carts up and down the aisles.
I think we forget how important transporting physical media (usually just paper) was back in those days. The penny post used to deliver twice a day in cities. Now I check my mail every 4-6 weeks and there's rarely anything important in it.
I suspect it's not the use of the bomb that is the biggest concern.
I would think someone with a bomb on some kind of bulk Hazmat carrier and the threat of blowing it up would shut down traffic for a lot longer. Nobody is going to want to get close to do anything about it.
LNG or Oil are the two I can think of, but there's probably a lot of other bulk Hazmat carriers.
The major canals aren't around big population centers so blowing something like that up wouldn't make a huge impact. Also due to the structure of a canal (limited blast containment; most of a ship is above the surface) the actual damage would be limited.
Blow up the locks for the Panama Canal and you have some seriously inconvenienced shipping companies.
But even in both cases the result is that they have to take the long way around. It makes the shipping slower and more expensive, but it was a tiny fraction of your costs to begin with so most companies survive just fine.