Hiya who! Nice stylisation on a lot of these. I like the watercolours. I'd recommend working on your anatomy some more(maybe some on the hands and feet?) and keep up the gesture sketches...your lines are getting looser already
(I keep reading the title of this thread as "Whose sketchbook? Aquaman's!")
For the Aquaman you should maybe do some more research on arm muscles, and maybe make his hands less angled(?) if that makes any sense. I like the outfit you've drawn on him, especially his belt.
I had an impossibly long comment here but my computer deleted it. hmph.
I like the blond guy with the dress shoes, he remind me of this.
“If you trust in yourself, and believe in your dreams, and follow your star, you’ll still get beaten by people who spent their time working hard and learning things and weren’t so lazy. Goodbye.” - Terry Pratchett