It is really easy to think of the Church as God’s palace and, therefore, baptism as God’s moat.
(Especially if you realize that the record of Solomon building God’s “Temple” and then his own “Palace” is a somewhat arbitrary English addition to the text. In the Hebrew, Solomon simply first build’s God’s great house and then his own great house. So all the passages about the Church as Temple of God could just as easily be about the Church as Palace of God, even though the language is Greek rather than Hebrew at that point.)
Crossing a boundary marked by water is labeled a baptism: “our fathers were all under the cloud, and all passed through the sea, and all were baptized into Moses in the cloud and in the sea” (1 Corinthians 10.1, 2).
And if crossing the Red Sea was a baptism, then so was the crossing of the Jordan, which included memorial signs and circumcisions at the next camp site (Joshua 3-5). And lets not forget the transition at the crossing of Zered. From Deuteronomy 2:
And we turned and went in the direction of the wilderness of Moab. And the Lord said to me, ‘Do not harass Moab or contend with them in battle, for I will not give you any of their land for a possession, because I have given Ar to the people of Lot for a possession.’ (The Emim formerly lived there, a people great and many, and tall as the Anakim. Like the Anakim they are also counted as Rephaim, but the Moabites call them Emim. The Horites also lived in Seir formerly, but the people of Esau dispossessed them and destroyed them from before them and settled in their place, as Israel did to the land of their possession, which the Lord gave to them.) ‘Now rise up and go over the brook Zered.’ So we went over the brook Zered. And the time from our leaving Kadesh-barnea until we crossed the brook Zered was thirty-eight years, until the entire generation, that is, the men of war, had perished from the camp, as the Lord had sworn to them. For indeed the hand of the Lord was against them, to destroy them from the camp, until they had perished.
So as soon as all the men of war had perished and were dead from among the people, the Lord said to me, ‘Today you are to cross the border of Moab at Ar. And when you approach the territory of the people of Ammon, do not harass them or contend with them, for I will not give you any of the land of the people of Ammon as a possession, because I have given it to the sons of Lot for a possession.’
So crossing over/through water seems to be the way one gets into the Kingdom. This is related to baptism and fits into our moat analogy…
But it doesn’t keep enough people out to really qualify as a moat. Frankly, baptism is more like the drawbridge. The whole point of baptism is how many people that it includes.
1 Corinthians 10:
For just as the body is one and has many members, and all the members of the body, though many, are one body, so it is with Christ. For in one Spirit we were all baptized into one body—Jews or Greeks, slaves or free—and all were made to drink of one Spirit.
For the body does not consist of one member but of many. If the foot should say, “Because I am not a hand, I do not belong to the body,” that would not make it any less a part of the body. And if the ear should say, “Because I am not an eye, I do not belong to the body,” that would not make it any less a part of the body. If the whole body were an eye, where would be the sense of hearing? If the whole body were an ear, where would be the sense of smell? But as it is, God arranged the members in the body, each one of them, as he chose. If all were a single member, where would the body be? As it is, there are many parts, yet one body.
The eye cannot say to the hand, “I have no need of you,” nor again the head to the feet, “I have no need of you.” On the contrary, the parts of the body that seem to be weaker are indispensable, and on those parts of the body that we think less honorable we bestow the greater honor, and our unpresentable parts are treated with greater modesty, which our more presentable parts do not require. But God has so composed the body, giving greater honor to the part that lacked it, that there may be no division in the body, but that the members may have the same care for one another. If one member suffers, all suffer together; if one member is honored, all rejoice together.
Now you are the body of Christ and individually members of it.
If someone wants to start a movement, it is easy to see benefits in raising “the cost of admission” to make sure you get committed people and entice coinverts by the prospect of being able to count themselves heroes. But God doesn’t ask us to swim through deadly waters. He just invites us with a bit of Spiritual moisture.
The heroic effort comes later, mainly in the form of the challenge of welcoming and loving one another, even the “least.”