As he stood / below the shower / the sharp jets of / ice cold water revived his spirit.

Ice cold water = redundancy. Cold water correct i think

Ice cold water must be change to ice water

why we use below instead of under?

Normally, Spirit is noun which means soul or non physical part of a man or person (Sometimes, it also used as an adjective.). In other hand, Often Spirits is a person's mood or attitude. So, in above given sentence, revival of the mood of a person is quite suitable. See these examples:

1. The warm weather lifted everyone's spirits.

2. He confessed in a spirit of self-respect

Spirits is not right word here. Checked by the hard rule of grammar also, spirit is right. If you don't agree, provide the reason.