If you are still in winter here is a lovely warm summer day on a bird reserve on the south coast of England.
I usually cycle here and then you have to walk along the coast for a while. It is very secluded on the beach side.
The sand flats go out in to the shallow sea and the water is usually nice and warm (for England). You can leave your bike unlocked and it won’t get stolen. I go for a leisurely swim and watch the sailing boats go by.