Place the cranberries and sugar in a blender or food processor. Blend until smooth, scraping down the sides as needed.
Drain the crushed pineapple in a colander, pressing on the fruit to extract as much liquid as possible. Add the cranberry mixture, crushed pineapple and cocowhip to a bowl. Gently fold to combine. Add the marshmallows and gently stir in.
Pour the mixture into a serving dish. Let sit for at least 6 hours and up to overnight. Top with pomegranate seeds. Enjoy!