Two temporary dams across the canal, above and below the ship; basically creating a temporary lock in the canal. Sandbags and tarpaulin, or two huge balloons you fill with water so they squeeze themselves stuck against the sides. (In both cases, with suitable temporary support structures on the outer sides. For a base, use a big empty ship or three on each end, run them up against the dam and scuttle them, then refloat when all is done?) Then fill the lock you just built with water pumped in from the canal, and the ship should float. When it's upright in the middle of the canal, dismantle the lock again. It doesn't have to be all that super tight or anything; as long as your pumps can outrun the leakage, just keep running them for the duration.

The GP is only the second such suggestion I see here. The first was on the second sub-page of comments (close to a comment about lifting the ship with a hydrogen balloon, for a search term; combining them is where I got the water balloon idea in stead of sandbags). Mine would have been the third.

Quite honestly and seriously seems far from unfeasible. And perhaps, depending on how fast you can get enough sandbags (or just the bags; sand should be available nearby?), tarpaulins, and pumps there, faster than most other suggestions.