In discussing the modes of baptism in the New Testament, it's good to think about why St. John the Baptist used the river Jordan for baptizing.
It's true that he was out in the wilderness. It's also true that Palestine is a land without a lot of water (then as now) and the river would have provided a ready source of water for the washing of baptism.
Another good thing to remember is that since the Bible is inspired by the Holy Spirit, we can start off with the assumption that the words are significant. God speaks to us in words. Not in pictures, not in dreams, not in visions, but in words.
So there's a reason why the river Jordan is mentioned. The writers (and the Holy Spirit who inspired them) could have simply said, "He baptized them." But we're told that it was in the river Jordan.
The New Testament points backward (calling us to remember and ponder our forefathers in the faith in the Old Testament) as well as forward, when Christ commands that his gospel be preached throughout all the world. The Jordan's especially important because of the story (in the book of Joshua) when the people of Israel pass through the Jordan on dry land when the waters were parted. So the children of Israel were saved through the waters of the Jordan. So Christ makes holy not just the waters of the Jordan, but all waters when he is baptized there.
Others in the New Testament were not baptized in the Jordan -- think about the 3,000 baptized in Jerusalem on the day of Pentecost, the Ethiopian treasurer who was baptized at a Wadi in the desert in Acts 8, and the jailer baptized in the jail itself in Acts 16. (We sometimes think of Jerusalem as being close to the Jordan, but the river's no less than 20 miles away, and there's no indication that the 3,000 went there that day).
We can be thankful that the Holy Spirit chose to specifically indicate that these folks were not baptized in the Jordan. Because if they had, we might think our baptisms less important because we were baptized somewhere else. The tie between St. John's baptizing in the Jordan and the historical ties to the Jordan for the people of Israel are important. But wherever you were baptized -- in a hospital, in a church, in a swimming pool, a river, wherever -- your baptism was and is a washing away of your sins: one that you remember because Christ promised his blessing there, the blessing of union with God and life eternal.