Mersea Island is about 8 miles south of Colchester. The only road access is via the Strood, a causeway that floods at high tide — check tide tables before you visit to avoid being cut off. Colchester is served by fast trains from London Liverpool Street (about 50 minutes). From Colchester, take a taxi or the 62/64 bus to West Mersea; the journey takes around 30 minutes by road. There is no train to the island.
By car from London, take the A12 to Colchester and then the B1025 south to the island. Parking is available at the West Mersea waterfront but fills up quickly in summer.