These were sketched with my water soluble sailor fude pen (hehe it's obviously the ink that's water soluble, not the pen - that would be tricksy to use in the extreme). If you haven't seen one of these pens in action, search for the White Rabbit on YouTube, she does some amazingly inspirational work with one.
This next one was the view from our hotel balcony in Los Cristianos. The surface I used is kitchen paper glued down with PVA. It's very absorbent so the paint moves around super quick, which makes for a lovely loose sketch.
Water soluble pen and Gouache.