The Littorina saxatilis complex of species is a fascinating example of speciation in action, including elements of strong environmental selection gradients operating both within species and between species.We aim to generate 30x Illumina resequencing data (Illumnia WGS) for individuals of L. saxatilis "wave" and "crab" ecotypes, L. saxatilis neglecta, L. saxatilis tenebrosa and Littorina arcan. In addition, we would like to test the comparative utility of haplotagging resequencing for population genetics in this complex by haplotagging sequencing of a subset of the L. saxatilis "crab" and "wave" ecotypes, taken from the individuals processed for Illumna WGS. This work is part of the Darwin Tree of Life efforts.