The Commewijne district across the river from Paramaribo is a half-day trip: the old coffee and cacao plantations at Frederiksdorp and Rust en Werk, the fort at Nieuw Amsterdam, and — at the confluence where the Commewijne meets the Suriname — a resident group of Guiana river dolphins.
Boats leave from Leonsberg on the Paramaribo side, and the dolphin trips are timed for late afternoon when the animals are feeding and the light is worth having.
Crossing under your own steam. Besides the organised tours, small boats cross the river all day from Leonsberg to Nieuw Amsterdam, and on the other routes — Paramaribo to Meerzorg, Domburg to Laarwijk. There is generally somebody at the landing willing to take you across; you agree the fare on the spot and pay cash. None of these boatmen advertise or take bookings, so it is a matter of turning up rather than arranging anything in advance.