Mark 16:15, 16,
"15 And He said to them, “Go into all the world and preach the gospel to every creature.
16 He who believes and is baptized will be saved; but he who does not believe will be condemned."

1Pet 3:21: "There is also an antitype which now saves us - baptism (not the removal of the filth of the flesh, but the answer of a good conscience toward God), through the resurrection of Jesus Christ."

Note that in our text it does not say that the one that is not baptised will be lost - it says the one that does not believe will be lost.

Water can never save us. The thief on the cross received Jesus' salvation through faith without being baptised.

If you believe on the Lord Jesus Christ by the grace of God you shall be saved. We've read in Peter's epistle that water cannot wash away the filth of the flesh.
It is faith in the Lord Jesus that saves us. Being baptised without faith profits you nothing. There must be faith. If you are baptised but do not believe in Him it profits you nothing.

Paul says that he thanks God that he did not baptise many people, for the Lord did not send him to baptise but to preach the Gospel. No baptism of any sort will profit you anything unless it goes along with faith in the Lord Jesus.

Faith without works is dead. Faith is a living entity which produces life and good works. But good works cannot save you. We read in Mark of the works that will follow those who believe. There are signs, the works of faith which show and prove that a person has believed.

John the Baptist said to the scribes and pharisees who came to his baptism of repentance (Matt 3:7), "You brood of vipers! Who warned you to flee from the coming wrath? Produce fruit in keeping with repentance." So there must be the fruit of your repentance and faith. New life must appear otherwise your faith is worthless.

Louis Harms preached that those who are baptised but do not show the fruit of faith will receive a double hell.

Faith in Jesus Christ is of utmost importance. Without believing in Him you are spiritually dead. Faith comes by hearing the Word of God. How will people hear if they are not preached to?

In 1Pet 3:20, we read that even in the days of Noah they were saved through water. This is an anti-type, a symbol of salvation which must come first. Not that baptism saves you, but only as a sign of a clear conscience. It clearly states that baptism cannot wash away the filth of the old man, the flesh. We read in Gal 5:19-21 what these works of the flesh are, "Now the works of the flesh are evident, which are: adultery,  fornication, uncleanness, lewdness, idolatry, sorcery, hatred, contentions, jealousies, outbursts of wrath, selfish ambitions, dissensions, heresies, envy, murders, drunkenness, revelries, and the like; of which I tell you beforehand, just as I also told you in time past, that those who practice such things will not inherit the kingdom of God." Water baptism cannot cleanse you from these things. Only the wonderful precious Blood of the Lord Jesus Christ can cleanse you from the works of the flesh.

This water baptism is the confession of a good conscience before God.

If you envy, gossip, fight, argue, etc., then no waters are able to cleanse away those things. You need to be cleansed by His blood, and then your conscience will be clear and you can be baptised with a clean conscience before God.

In the same way with the Table of the Lord, you need to come with a clean conscience that there is nothing between you and the Lord and between you and your brother or sister. The bread and wine symbolises that we are one in Christ. Should you participate in the wine and bread while having a grudge against someone you are condemning yourself and it will be a curse to you and not a blessing.

So too if you are baptised but do not truly believe, you have only a dead faith, you are condemning yourself.

There is a woe upon those who go through all the rites of baptism but do not live the new life.

In the Old Testament we read that those who are not circumcised are not part of God's people. Under the new covenant Paul wrote that it is not circumcision or uncircumcision but a new creation in Christ which counts.

Men, when you are baptised you testify that you have parted with anger. Ladies, you testify that you have parted with jealousy, gossip and slander. You also testify that you have parted with any form of pornography, whether on the internet, magazines etc.

Maybe you think yourself as more important than others and insist that things must be done your way. Then you are on the wrong road. Jesus said that he who wants to be the greatest must be the servant of all.