What anxieties came about for Pi at the end of the day?

From the text:

As evening approached, my anxiety grew. Everything about the end of the day scared me. At night a ship would have difficulty seeing me. At night the hyena might become active again and maybe Orange Juice too.

Darkness came. There was no moon. Clouds hid the stars. The contours of things became hard to distinguish. Everything disappeared, the sea, the lifeboat, my own body. The sea was quiet and there was hardly any wind, so I couldn't even ground myself in sound. I seemed to be floating in pure, abstract blackness. I kept my eyes fixed on where I thought the horizon was, while my ears were on guard for any sign of the animals. I couldn't imagine lasting the night.