Method for transport and installation of objects at sea, particularly relating to transport and installation of obs jects that are part of the infrastructure in oil and gas fields offshore, the object (4) is put in the sea at a suitable location near the shore or in sheltered waters, then towed to the installation site while being suspended in a slender buoyancy unit (5) acting much like a heave compensating unit. Upon arrival at the installation site, the suspension of the object (4) is transferred from the buoyancy unit (5) to a heave compensated winch (3) on a surface vessel (2), preferably the same vessel as used for the preceding towing operation. The winch is used to lower is the object (4) to its destination on the sea bottom or a predetermined location above the sea bottom.