Lower Strange is the Canal District. Some of them actually are purpose-built canals, but many are simply flooded streets, lined with half-drowned buildings (and in some places completely drowned, like Teatr Subantegk).
If you're not from around here, you probably don't want to go for a swim. The water is shot through with swirls of metallic colour and eerily glowing traces. Plenty of things live down there too, though it's too opaque to see them... probably a mercy.
Water flows down into the canals from Top and Down (the latter supplying it with plenty of hazardous chemicals), and the same black boats that ply the Arha can be seen in Strange.