Even though this is for summer, I would do this every time of the year. In autumn/winter wrapped up in a blanket with a hot drink and toasting marshmallows and in summer/spring sitting on the beach watching the night unfold.
Tiny House by BF Architects. This tiny house on the banks of the Eel river in Plymouth is less than 400 square feet and has a kitchen, full bath, living room, sleeping loft and screen porch! George Canavan of Plymouth was the builder.