Unidirectional walking from a seed clone C₀. Each successive clone C_i extends the island, with the redundant sequence shown in grey. The last clone C_j closes the ocean, with redundant sequencing due to both overlap with C_j-1 and with the next seed clone to the right. Each clone has size 1, and the ocean has size X. The number of clones sequenced isj + 1, with each having length 1. The amount of unique sequence obtained (the initial island together with the ocean) isX + 1.