All times are in Greenwich Mean Time, so please add one hour during British Summer Time (daylight saving).
Digimap hosts a tide calculator for all Guernsey Harbours' operated marinas, Beaucette Marina and Herm Harbour.
Guernsey tide tables can be found on the States of Guernsey's website by clicking here.
Alderney tide tables can be found on Visit Alderney's website.