Pope Eugene IV, Council of Florence, "Cantate Domino," 1441, ex cathedra: "The Holy Roman Church firmly believes, professes and preaches that all those who are outside the Catholic Church, not only pagans but also Jєωs or heretics and schismatics, cannot share in eternal life and will go into the everlasting fire which was prepared for the devil and his angels, unless they are joined to the Church before the end of their lives; that the unity of this ecclesiastical body is of such importance that only for those who abide in it do the Church's sacraments contribute to salvation and do fasts, almsgiving and other works of piety and practices of the Christian militia produce eternal rewards; and that nobody can be saved, no matter how much he has given away in alms and even if he has shed blood in the name of Christ, unless he has persevered in the bosom and unity of the Catholic Church." [1,2,5]
Look closely at this paragraph immediately above and one sees two basic parts, the first that teaches that "all those who are outside the Catholic Church, not only pagans but also Jєωs or heretics and schismatics, cannot share in eternal life and will go into the everlasting fire which was prepared for the devil and his angels, unless they are joined to the Church before the end of their lives" (in other words, dealing with those who are outside the Church, and the second, "that the unity of this ecclesiastical body is of such importance that only for those who abide in it do the Church's sacraments contribute to salvation and do fasts, almsgiving and other works of piety and practices of the Christian militia produce eternal rewards; and that nobody can be saved, no matter how much he has given away in alms and even if he has shed blood in the name of Christ, unless he has persevered in the bosom and unity of the Catholic Church," which deals with those who are inside the Church. Notice that it is clearly referring to the second part (those inside the Church) when it uses the word "persevered" to specify what they must do. To sacrifice all and give any manner of alms etc. but then fail to persevere within the Church is to be in that category in which "nobody can be saved." Only the first part of this paragraph pertains to those who are outside the Church (and hence required to seek baptism), and the only condition it places upon them is to be "joined to the Church before the end of their lives." Since this does not in any manner address what it takes to be "joined to the Church" it in no way excludes whatever means God may elect to use in some specific case where water baptism was not obtainable but nevertheless sought.