I would like to know the scale.
The islands are good, not to geometrical, but the coast seems straight. But then again, if its an inner sea like the Mediteranean then maybe this could work. No specialist myself, but I tend to have less shattered shores inside a continent than on the outside where all the waves of the ocean can come and affect the landscape.
Now, a suggestion of mine which you can discard if you so desire...
I would see your city being gifted with either a natural opening for ships or a man-made larger cannal than what you already have in order to facilitate sea trafic and, also, allowing a defensive fleet to patrol. I do know that you have little cannals and three ''Main Cannals'', but I doubt the small canals are large enough to allow a Caravel class ship to pass by, which is logical indeed, but I doubt you could have several battleships traveling back and forth BETWEEN the islands.
I would also have some light house on the small island to the west to warn big ships in the night.
Concerning the different canal plannings, I would suggest before laying them out to place at least the most important buildings first and from THERE planning your canals. Keep in mind that a city won't make roads just for the look. I would diminish the number of tiny canals opening on the outside of your city, but keep a good number connecting to the bigger cannals. Small ships won't be traveling across the ocean, but they are likely to cross from one island to the other.