A shipper is transporting 150 gallons of a liquid listed in Appendix B to Sec. 172.101 as a marine pollutant, in a single bulk container, and the material does not otherwise require a placard or label. What is required?

49 CFR 172.322(b) (marine pollutant marking requirement for bulk packaging); 49 CFR 172.322(e) (mark design: square-on-point/diamond shape, black fish-and-tree symbol on white or contrasting background); 49 CFR 171.8 (marine pollutant definition)

Marine pollutant marking exists specifically to protect waterways from spills during transport even when the material isn't hazardous enough to need a placard, so skipping it on a qualifying bulk shipment is a real, citable violation separate from any hazard-class marking.