Enthrilled

It could be that the ship is a spaceship, the whirlpool is a black hole, and the islands are planets. Derithil would be searching for the planet where the “voidbringers” are imprisoned between returns. Another option would be that he is looking for the lost/destroyed planet Earth. Derithil and his crew leave into a high storm but this seems to be one of the more questionable distinctions in Wit’s story; maybe the high storm in Roshar is just a smaller version of a larger storm happening in the cosmere. Either way the crew are propelled uncontrollably towards a mystery destination where they crash and are rescued by strangers. I like to assume that those people still follow the same fundamental laws as every other being in the universe be they shard or mortal. The anecdote seems to me to be a masterful hint at the extent of the universe in which Caladin suffers for the reader but at the same time a turning point for Cal in his journey. It is known that the high storm does not blow strongly in Shadesmar, which is why I do not see Derithil in the cognitive realm. Also it is implied later on in the series that the power of Dalinar to create the unity was not an ability until after Honor’s death so it is unlikely that Derithil would be traversing through one of those unless he went with Honor’s blessing. If Derithil was an honor sprin then I could see him starting his journey in the cognitive realm and never leaving it but if he was a human or singer I see no reason why he would be traveling on a ship into shadesmar.