For me, plein air painting [French- for open air painting] is all about relaxing and not necessarily achieving a perfect masterpiece. Mostly the sketches I start outside will be the smaller studies for larger pieces. But sometimes it's nice to just get out and be in the sun with your pencils and brushes.
Here's my array of watercolor brushes
Drawing pencils, sharpener, favorite pens (pilots), and sharpies
Bucket for water. Whenever I go sketching at the beach I never bring my own water but use salt water and let the salt work with my watercolors.
To keep things simple I use a tray of watercolors instead of my usual tubes.
My bag to carry everything in.
And music, its sets the mood.I did a few rough drawings of some seagulls and herons, I'll definitely be going back hopefully next time I'll get to spend more time out there.