For me, what was really interesting or surprising is that they did not have enough water even though the city itself is surrounded by water. Also, some people did not have toilets and had to pay for public toilets.
Even though it is slums we are talking about, and we know how terrible the conditions are, still there's always some surprises (negative ones unfortunately). Specifically in Mumbai, it is surprising that big portion of the people living in the slums do not have access to city services, they do not have enough water even thought the city itself is surrounded by water, more then half of the population of Mumbai lives in slums (around 55%), most of the residents do not have toilets and have to pay for public toilets...