If you've never tried sea kayaking, kayaking from the shore to the sea enables you to experience the water in a new way. You have to work with the currents in order to move forwards, and feel them rocking your boat along the way, becoming one with the water.
On the days when the wind takes a break, you can see every detail of the sea underneath you, the clear white sand at the bottom, and all of its inhabitants.
Summer means dolphin season in Ogasawara. By going out to sea with a guide, you will be able to go look for them thanks to the insight that they have on where the dolphins are. You will then be able to dive several times — with snorkeling gear — right next to the dolphins and swim with them for a bit! Since they are not hunted or threatened by the islands' inhabitants, they don't fear people and you can get very close to them.
My personal highlight. Even with no scuba diving experience, you can go snorkeling on some of the world's most beautiful beaches and creeks, surrounded by hundreds of curious, colourful fish, seashells, corals, turtles, stingrays, jellyfish and so, so many more.
With swimming allowed from January 1st to December 31st, don't worry about missing the season!