I spent a week on Bonaire - drawing under and above water, scuba diving, kayaking in mangrove forest and enjoying wind, sun and a little bit of rain.
My current sketchbook traveled with me (#103) - it's is an 8.5" x 8.5" square kunst-papier sketchbook with a very soft paper. I hoped that it would be a good option for gouache as I found it recommended by an amazing illustrator who uses it a lot - Leah Goren but I think it's not strong enough for my layering and re-working experiments. Is's great for ballpoint pen and markers. I use a lot of paint in it and it's great if everything worked on the first layer!
I used rite-in-the-rain paper for these underwater sketches and a wonderful 2B mechanical pencil without metal parts and taped these sketches in my sketchbook after washing salt water off and drying them thoroughly.
You will find some notes on that I saw as well as basic communication with my dive buddy.