The first to use steamships for internal trade in Calcutta, he prospered in competition with Europeans. He owned around thirteen trade ships including a steam tug named "Banian". He made a fortune in a single generation through money-dealing, which includes lending, bill counting and other banking business. There was scarcely a speculation into which he did not enter, and for which he did not supply a portion of funds. From dealings in internal exchanges to contracts for station-building, for the erection of new bazaars, to the revival of transit companies, rare was an undertaking in which he was not an important, though quiet, shareholder. He funded every promising enterprise he found and made profits in the shape of interest. At one point he was in complete control over the market dealing in company papers. Seal was one of the founders of Assam Company Ltd.