not, have not, none, to drown, sink
沒 centers on disappearance or absence: sinking below a surface, drowning, or the state of not having something. The 'not' and 'none' senses are abstract extensions of something being submerged and lost from view.
沒 combines 氵 (water) with a phonetic element that historically represented submersion. The character originally depicted something sinking or disappearing into water, which extended to the abstract sense of absence.
The left side is water 氵, and the right side looks like a hand 又 reaching up while being pulled under by a force 力. Picture something sinking into water, disappearing from sight—just like drowning or having nothing left.
For ボツ, imagine a boat sinking into the water with a deep 'botsu' sound as it goes under: botsu -> ボツ, and the boat disappears beneath the surface.