See a torii standing out in the sea
Torii are the gates that mark the way into a shrine, and a few stand out in the sea, facing shrines on the shore. At high tide the water rises around their pillars; at low tide you can sometimes walk right up to them. Check the tide tables before you go.
A torii on a reef where the gods are said to have come ashore, with Pacific waves breaking at its feet. It is famous at sunrise, when the sun comes up behind the gate; the reef is off-limits, so watch from the seawall. About 2 hours from Tokyo by train, changing at Mito.
The great torii of Itsukushima Shrine on Miyajima, 16.6 m tall, is not buried in the seabed but stands under its own weight. At high tide it seems to float on the sea, and at low tide you can walk across the sand to its base. Miyajima is 30 minutes by train and 10 minutes by ferry from Hiroshima, with a 100-yen visitor tax added to the ferry fare.
Three torii stand in a line out into the Ariake Sea, where the tide rises and falls by up to 6 m, among the largest ranges in Japan. They sink under water at high tide and stand on bare mudflats at low tide, so check the tide tables for the time you want to see.