Sublimotion

Dry ice is denser than water and generally sinks but I noticed that a small enough flat piece not only floats, it hovers on the cloud of vapor between itself and the water and bounces back and forth across the container with only a tiny nudge.
This got me to thinking that it may be possible to make a boat using this principle with two hulls. A perforated outer hull and a water proof inner hull with nozzles evenly distributed across its surface.
Liquefied CO2 would be released from the inner to the outer hull, the dry ice snow displacing the water and collecting on the matrix provided by the perforations.

When the outer hull has been entirely encased in the snow it will create a barrier of steam between itself and the water, rendering the hull nearly frictionless with no impediment to forward motion.
The heat from the inner hull will cause the dry ice to also sublimate a layer of carbon dioxide gas between itself and the inner hull so that more of the liquid can be released.
The boat would actually sweat dry ice.
Because the CO2 snow is not rigid, a flexible outer hull might allow for some laminar flow, and if the inner layer's waste CO2 was collected and re-compressed on board, the excess heat could run a Sterling engine which powers the boat.