FR. ALOYSIA SABETTI, S.J., FR. TIMOTHEO BARRETT, S.J., Compendium Theologiae Moralis, Tractatus XII [De Baptismo, Chapter I, 1926:
Baptism, the gate and foundation of the Sacraments, in fact or at least in desire, is necessary for all unto salvation...
>From the Baptism of water, which is called of river (Baptismus fluminis), is from Baptism of the Spirit (Baptismus flaminis) and Baptism of Blood, by which Baptism properly speaking can be supplied, if this be impossible. The first one is a full conversion to God through perfect contrition or charity, in so far as it contains an either explicit or at least implicit will to receive Baptism of water... Baptism of Spirit (flaminis) and Baptism of Blood are called Baptism of desire (in voto).