See: Kolkata#Get_around
To zip around between Kolkata and Howrah the ferry service to cross the river Hoogly is very good. There are a number of Banks on the other side and the ferries go to such as Armenian, Fairlie, Chandpal, Babughat, Princep. The fare per head is Rs 4, buy the ticket before you board the ferry and retain the ticket till after you have crossed to the other side and have shown it to the ticket checker near the Exit gate or else you will be fined!