The necessity of water Baptism for salvation is attested to by the Early Church Fathers and Scripture.
The early Christians and ECF’s (Early Church Fathers) were big on water baptism even though the method could very. In winter you could substitute the river with pouring water over someone’s head three times. But it always involves water.
ECF…Tertullian on Water Baptism (155-220 ad)
Happy is our sacrament of water, in that, by washing away the sins of our early blindness, we are set free and admitted into eternal life! A treatise on this matter will not be superfluous; instructing not only such as are just becoming formed (in the faith), but them who, content with having simply believed, without full examination of the grounds of the traditions, carry (in mind), through, an untried though probable. The consequence is, that a viper of the Cainite heresy, (Gnostic) lately conversant in this quarter, has carried away a great number with her most venomous doctrine, making it her first aim to destroy baptism. Which is quite in accordance with nature; for vipers and asps and basilisks themselves generally do affect arid and waterless places. But we, little fishes, after the example of our ΙΧΘΥΣ Jesus Christ, are born in water, nor have we safety in any other way than by permanently abiding in water; so that most monstrous creature, who had no right to teach even sound doctrine, knew full well how to kill the little fishes, by taking them away from the water!
Tertullian on why Water Baptism
Mindful of this declaration as of a conclusive prescript, we nevertheless proceed to treat (address) the question, How foolish and impossible it is to be formed anew by water. In what respect, pray , has this material substance merited an office of so high dignity? The authority, I suppose, of the liquid element has to be examined. This however, is found in abundance, and that from the very beginning. For water is one of those things which, before all the furnishing of the world, were quiescent with God in a yet unshapened state. In the first beginning, says Scripture, God made the heaven and the earth. But the earth was invisible, and unorganized, and darkness was over the abyss; and the Spirit of the Lord was hovering over the waters. The first thing, O man, which you have to venerate, is the age of the waters in that their substance is ancient; the second, their dignity, in that they were the seat of the Divine Spirit, more pleasing to Him, no doubt, than all the other then existing elements. For the darkness was total thus far, shapeless, without the ornament of stars; and the abyss gloomy; and the earth unfurnished; and the heaven unwrought: water alone — always a perfect, gladsome, simple material substance, pure in itself — supplied a worthy vehicle to God. What of the fact that waters were in some way the regulating powers by which the disposition of the world thenceforward was constituted by God? For the suspension of the celestial firmament in the midst He caused by dividing the waters; the suspension of the dry land He accomplished by separating the waters. After the world had been hereupon set in order through its elements, when inhabitants were given it, the waters were the first to receive the precept to bring forth living creatures. Water was the first to produce that which had life, that it might be no wonder in baptism if waters know how to give life. For was not the work of fashioning man himself also achieved with the aid of waters? Suitable material is found in the earth, yet not apt for the purpose unless it be moist and juicy; which (earth) the waters, separated the fourth day before into their own place, temper with their remaining moisture to a clayey consistency. If, from that time onward, I go forward in recounting universally, or at more length, the evidences of the authority of this element which I can adduce to show how great is its power or its grace;; how many ingenious devices, how many functions, how useful an instrumentality, it affords the world, I fear I may seem to have collected rather the praises of water than the reasons of baptism; although I should thereby teach all the more fully, that it is not to be doubted that God has made the material substance which He has disposed throughout all His products and works, obey Him also in His own peculiar sacraments; that the material substance which governs terrestrial life acts as agent likewise in the celestial.
But it will suffice to have thus called at the outset those points in which withal is recognized that primary principle of baptism — which was even then fore-noted by the very attitude assumed for a type of baptism — that the Spirit of God, who hovered over (the waters) from the beginning, would continue to linger over the waters of the baptism. But a holy thing, of course, hovered over a holy; or else, from that which hovered over that which was hovered over borrowed a holiness, since it is necessary that in every case an underlying material substance should catch the quality of that which overhangs it, most of all a corporeal of a spiritual, adapted (as the spiritual is) through the subtleness of its substance, both for penetrating and insinuating. Thus the nature of the waters, sanctified by the Holy One, itself conceived withal the power of sanctifying. Let no one say, Why then, are we, pray, baptized the very waters which then exited in the first beginning? Not with those waters, of course, except in so far as the genus indeed is one, but the species very many. But what is an attribute to the genus reappears likewise in the species. And accordingly it makes no difference whether a man be washed in a sea or a pool, a stream or a fount, a lake or a trough; nor is there any distinction between those whom John baptized in the Jordan and those whom Peter baptized in the Tiber, unless withal the eunuch whom Philip baptized in the midst of his journeys with chance water, derived (therefrom) more or less of salvation than others. Act 8:26-40 All waters, therefore, in virtue of the pristine privilege of their origin, do, after invocation of God, attain the sacramental power of sanctification; for the Spirit immediately supervenes from the heavens, and rests over the waters, sanctifying them from Himself; and being thus sanctified, they imbibe at the same time the power of sanctifying. Albeit the similitude may be admitted to be suitable to the simple act; that, since we are defiled by sins, as it were by dirt, we should be washed from those stains in waters. But as sins do not show themselves in our flesh (inasmuch as no one carries on his skin the spot of idolatry, or fornication, or fraud), so persons of that kind are foul in the spirit, which is the author of the sin; for the spirit is lord, the flesh servant. Yet they each mutually share the guilt: the spirit, on the ground of command; the flesh, of subservience. Therefore, after the waters have been in a manner endued with medicinal virtue through the intervention of the angel, the spirit is corporeally washed in the waters, and the flesh is in the same spiritually cleansed.