Some seem to be for redundancy, some bring power to municipalities (i.e. island cities) with limited power production capacity. There’s a list here https://en.m

Some seem to be for redundancy, some bring power to municipalities (i.e. island cities) with limited power production capacity. There’s a list here https://en.m.wikipedia.org/wiki/Submarine_power_cable https://en.m.wikipedia.org/wiki/Submarine_power_cable