What is the antonym of a raft?

There isn't a single perfect antonym for "raft" as it depends on the context. Here are a few possibilities, depending on what you want to contrast:

If you're thinking about a raft as a floating platform:

* Boat: A more complex and stable watercraft with a hull.

* Ship: A large vessel for sea travel.

* Submarine: A vessel designed to travel underwater.

* Land: The solid ground as opposed to water.

If you're thinking about a raft as a group of people:

* Individual: A single person.

* Solitary: Alone, not part of a group.

If you're thinking about a raft as something assembled from several parts:

* Solid: A single, unbroken structure.

* Monolithic: A single, unified entity.

Ultimately, the best antonym depends on the specific meaning you want to convey.