The white trail on the right edge seems to be that of the contrails of a jet plane flying in the lower edges of the stratosphere.
Hexagonal dots in the middle of the image are called reflection. They are caused by a source of bright light not far from the frame. In this case, judging by the shadow of the beach on the beach, the sun is just right and above the edge of the field of view. Although the sun is not in the picture, some of its light shines obliquely on the front of the lens. This light bounces inside the lens, causing stray light. The hexagonal shape is the result of the aperture diaphragm of your lens, which has six blades.
The best way to combat reflections caused by strong light sources out of the frame is to use a sun visor. If your lens is a zoom lens, the hood provides only optimal shading at the largest focal length. When zooming in, you may need to protect the sun's lens with the help of a piece of cardboard or other opaque material.