A magical
artifact that appears in at least one very popular
fantasy RPG. The folding boat is similar in concept to a
portable hole, a
bag of holding, and various weapons that fold up, collapse, or otherwise disappear into
negative space. The artifact
manifests as a full-sized boat of various appearances (raft, skiff, yacht...) which folds up into a small, flat paper item (or an
origami boat, or a parcel, etc.).
The important thing about this is it allows you to keep your large, unportable, unwieldy transportation with you at all times.