Water frontage
The largest single variable, and it is not a percentage.
On oceanfront, linear feet of direct Atlantic frontage is the dominant value driver. On riverfront, it is frontage plus water depth at the dock. Neither scales with the house. A 100-foot oceanfront parcel is a fundamentally different asset from a 50-foot one even if the structures are identical, and no interior renovation closes that gap.
This is also where listing language does the most damage. Oceanfront means the property line runs to the beach. Ocean view is a sightline that may cross land you do not own. Ocean access means neither. Each carries a materially different price, and an automated model cannot tell them apart because the public record often does not distinguish them.
Valuing frontage correctly means asking what the frontage enables: beach access and privacy on the ocean side, a specific vessel at a specific tide on the river side. Two properties with the same recorded frontage can support very different uses.