Most large predators retreat from cities. The water monitor does the opposite, because the qualities that suit it to mangrove and riverbank also suit a concrete canal: it swims and dives well, climbs, digs, and eats carrion, refuse, fish, rodents, crabs and eggs without much fuss.
Bangkok's Lumphini Park has held a well-documented urban population, periodically the subject of removal operations when numbers grew conspicuous. Colombo's canal network supports monitors that function as scavengers of organic waste. Adults commonly run one and a half to two metres in total length, much of that tail, and are considerably lighter than the bulk suggests.
The species is listed as Least Concern globally, but that masks heavy regional harvest: the water monitor has long been among the most traded reptiles in the world for its skin. Local declines from hunting sit alongside urban abundance, so a single global category describes the situation poorly. Whether city populations are self-sustaining or subsidised by immigration from surrounding wetlands is not well resolved.