You can ask local guides and tour for day-cruise (or several days' time) with meals and everything included. It's best to share a kelotok with friends, so traveling in a small group to this area is advisable.
Tanjung Puting can only be reached by the river. For day cruise, you might use speedboat if you're opting for speed. For several days' time, kelotok, to me, is the best choice.
Sitting in a kelotok, with winds brushing your cheeks and hair, admiring the blue oh-gosh-have-I-ever-seen-bluer-colors-than-this-one sky, squinting at the trees waiting for some wild animals to appear. Feeling drowsy yet afraid of closing your eyes lest you miss seeing something worthwhile. Ahhh. I miss kelotok already!
PS: Beware of kelotoklag. You have been warned! :))