The invention provides a subsea trencher (1) for arranging at least partly into the seabed a subsea pipeline (55) laying on the seabed, the subsea trencher comprising: • - at least one cart (5, 7) that separately carries at least one trench tool (9) and is configured to run along the subsea pipeline, wherein the trench tool is configured to work the seabed underneath the subsea pipeline; CHARACTERIZED BY • - a subsea support frame (3), that carries, separately from the cart, heavy subsea equipment connected to the trench tool for operating the trench tool, and wherein when the subsea support frame is fixed to the cart, the subsea trencher is configured to load at least substantially the assembled weight of the cart and subsea support frame onto the subsea pipeline as the subsea trencher runs on the subsea pipeline, when the subsea support frame is separate from the cart, the subsea support frame is configured to be suspended above the seabed or arranged beside the subsea pipeline at a distance from the subsea pipeline as the cart runs along the subsea pipeline.