The name is misleading: inland marine mostly insures property on land, not property on inland waterways. The line grew out of insuring goods in transit, and many of its forms cover property regardless of location.

Floaters: forms whose coverage moves with the property are called floaters. Mobility is a common feature because coverage tied to one location does not fit property that keeps moving. A road grader moved between job sites is a classic floater exposure. A retailer's stock kept at its only store is stationary property and belongs on a commercial property form instead.

California's definition: Insurance Code §103 defines marine insurance broadly. §103(a) reaches all personal property floater risks, and §103(c) includes precious stones, jewels and jewelry, whether used in business or trade or otherwise, and whether in the course of transportation or otherwise. That is why a ring worn every day, not just a shipment, can be written as inland marine.

Not every inland marine risk moves; bridges and towers are also written in the line. But portability is the common thread.