Recomended equipment for one day trip:

Necessary:
1) life vest.
2) waterproof lugage bag.
3) comfortable clothes and shoes.
4) raincoat.
5) second underwear, clothes, shoes.
6) sunprotection cup.

Remember:

1) Clothes, food, telephone and things which afraid of wet, must be packaged in waterproof bags.

2) Do not take things with you, which will not be required.