The acceptance into the Church should correspond to the reality. All of this must be determined in detail prior to accepting them into Orthodoxy. The reverse is also true. However, the Church has always accepted a baptism as being with grace in such cases when an immersion was not possible as in the case of illness or just prior to death. A contact with water in any form was acceptable.
Every priest knows of such cases, especially with babies.
Some Orthodox Churches, such as the Serbian church do not practice full immersion due to historical reasons. No one ever had the idea to say that all Serbians cannot be considered baptized or that they should all be re-baptized. The Orthodox Church has a special rule, which concerns all cases in which the condition is not clear. This is a conditional performance of a sacrament. In such cases anyone may be baptized.