Yes, the phrase "there is no one to trust who is not in the cave of the snake eel" means that crabs need to live in the cave of the snake eel because they don't have their own caves.

However, it should be noted that this does not mean that crabs can only live in the caves of snake eels, but because they need a safe place to live. Crabs can find caves in different waters, such as rivers, lakes or oceans. Crabs can avoid predators in these caves, and at the same time, they can protect themselves from the natural environment such as wind, rain and sun.

Generally speaking, crabs can't only live in the caves of snakes and eels, but they need a safe place to live.