There are many, many (some confusing) expressed differences between ship and boat, one of the pithier ones being
When a ship sinks you get in a boat, when a boat sinks you get in the water.
Submarines and ferries, as you noted, are boats. That would fit the above definition (most ferries don't have lifeboats) conveniently, but there has to be more. Some yachts, ferries, tug boats, fishing boats, police boats, etc. do carry small lifeboats or dinghies, but they usually don’t graduate to ship status because of that.
Per Mental Floss
Another factor the Naval Institute considers is the vessel’s crew, command, and use. If it has a permanent crew with a commanding officer, it’s usually a ship. If it’s only crewed when actually in use and has no official CO, then you’re probably dealing with a boat. Ships are also usually intended and designed for deep-water use and are able to operate independently for long periods of time. Boats, meanwhile, lack the fuel and cargo capacity for extended, unassisted operation.
The obvious exception to deep-water definition are the commercial fishing boats that go out for months in deep water. However, they don't have a fixed crew.