A good harbour crane always makes a desirable scenic item. You can even station a sniper or spotter on it. In 20mm play, my Dalpo crane saw plenty of action, and I even scratch built one for my 6mm harbour.
In N gauge they are too rich to buy, but I have just seen a neat Faller kit at £12.75 for a small portable crane No 222200 . It looks the business
Would it also work on a canal or is it too big?
Should be neat enough, it is designed to work trackside and has a short jib. I was going to scratch build a longer jib to look right in a docks setting.
Another version without the gantry legs is styled the 'load crane' No 232511,I saw on ebay at £5.50. It would go well with a canal.