The width of the Sanzu River is said to change depending on who is crossing it. The more you pay for your fare to the shinigami, the narrower the river becomes.

The fare paid is the sum of the deceased's wealth. This wealth does not refer to the money the deceased owns, but rather the sum of the money those close to the deceased spent on them before they died. If this amount is in the negative, the boat will never reach the other side of the river, and the shinigami will toss the deceased off the boat partway.

This river separating Higan and Shigan is known to everyone and can be accessed from the other end of the mountain. Shigan refers to the side of the river in Gensokyo, while Higan refers to the other side. The river is also filled with fish that have gone extinct, but it is impossible to catch them because they are all ghosts...

For some reason, you cannot swim across the Sanzu River. Bodies do not float in the water, so swimming itself is impossible. It seems the only thing that can cross the river is the shinigami's boat―everything else just sinks...

The river's current is weak, making it very quiet. Sometimes, you can hear the cheerful shinigami singing and chatting, but that is all. No other living creatures can be heard. Mysteriously, even the water is silent as the boat moves through it.