The history of insurance is intimately tied with the sea. Insurance pretty much started out as "marine" coverage. Later as items were taken off the boats and taken inland then "inland marine" coverage was borne.
Today Inland Marine pretty much refers to mobile equipment. Pretty much anything that is moved to the job site to do the work can be covered under Inland Marine coverage also referred to as Equipment Coverage. This type of coverage is Property Coverage and not Liability coverage. Liability covered relates to coverage for injury or damage resulting from the work performed. It can be coverage for Bodily Injury or Property Damage resulting from the work or the finished product. Liability coverage does not provide coverage for the equipment or property owned by the contractor.
In a similar sense Business Auto or Commercial Auto coverage is primarily a liability coverage. The Comprehensive and Collision or the Fire/Theft coverage are what cover the property itself (the actual vehicle being driven by the insured). This property portion of the coverage on the vehicle being driven is not mandated by law. This is also where there is what can be considered a bit of a gray area. A commercial auto policy can sometimes be set up to cover equipment, such as a welder permanently attached to the bed of a truck. But an auto policy does not usually include equipment such as a compressor, tools, etc. so don't assume that these items are covered against damage or theft.