The following from the Didache (c. 70-150 AD) is interesting;

Chapter 7. Concerning Baptism.

And concerning baptism, baptize this way: Having first said all these things, baptize into the name of the Father, and of the Son, and of the Holy Spirit, in living [running] water. (2) But if you have no living water, baptize into other water; and if you cannot do so in cold water, do so in warm. (3) But if you have neither, pour out water three times upon the head into the name of Father and Son and Holy Spirit. (4) But before the baptism let the baptizer fast, and the baptized, and whoever else can; but you shall order the baptized to fast one or two days before.

Note that the "correct" way was baptism in cold running water - with other options being considered a fall-back position.

The mention of the need to fast for one or two days before baptism provides the genesis for the modern tradition of Lent - Easter being the traditional time of baptism with the "one or two days" extended out to 40 days in more recent times.