A propulsion control system on a marine vessel includes at least one propulsion device configured to propel the marine vessel and at least one proximity sensor system configured to generate proximity measurements describing proximity of objects surrounding the marine vessel. A control system is configured to receive the proximity measurements, access a preset buffer distance surrounding the marine vessel, calculate a velocity limit for the marine vessel in one or more directions of the objects based on a difference between the proximity measurements and the preset buffer distance surrounding the marine vessel so as to progressively decrease the velocity limit as the marine vessel approaches the preset buffer distance from any of the objects, and control the at least one propulsion device such that a velocity of the marine vessel does not exceed the velocity limit in the direction of any of the objects.