The boat, coming from Pujali in South 24 Parganas district to Nepalighat, adjacent to a jute mill in Chengail area of Howrah, toppled as the boatmen failed to negotiate the tides when a small ship passed by, police said.
While the two persons were missing, 20 others were either rescued by boatmen of nearby vessels or swam ashore to safety, police said.
Unconfirmed reports, however, put the total number of people on board to 26 and said six were missing.