Question: Could you explain the last part of Mark 5:7 where the demon says to Jesus “I implore you by God not to torment me”? Also, where Jesus fed the 4 and 5 thousand, did the Lord supply their water too?
Response: The KJV has "I adjure you" instead of "implore", and that is a much better way to translate horkizo (ὁρκίζω) here, the verb from which we get the noun "exorcism". By using this verb, the subject (i.e., the demon in this context) is trying to place the object under the compulsion of the person (or Person in this case, namely God the Father) who is being appealed to, in the hope of getting just oversight and resolution of the issue at hand. We find something similar when the Jewish exorcists say at Acts 19:13, "I charge you by Jesus whom Paul preaches". This is actually a pretty good parallel to Mark 5:7 (same exact verb form in every respect), because in both cases the person making the appeal has no "in" with the Person appealed to - no matter what formula the demon or the unbelieving exorcists used, the Father is not going to be put under any obligation to respond (and so neither is the person or Person being addressed). But that, surely, was the hope in both cases. Of course our Lord cast out many demons, and so did the apostles. In Acts 16:18, Paul commanded the demon “in the name of Jesus Christ” to leave the “girl with the familiar spirit” (Acts 16:16). As an apostle, he had the gift or power of exorcism. Notice He didn't need to use the verb orkizo as in the two cases above, but invokes the Name of the Savior so that all will understand who is providing the power for ejecting this demon. Finally it ought to be noted here too that orkizo which forms the basis for our word “exorcism” occurs only in these two passages of scripture (i.e., Mk.5:7 and Acts 19:3), two cases of ineffective “adjuring” where a mere formula invoked in a sort of “magical incantation” fails to produce the desired result. This should give us pause whenever we hear of “exorcisms”, because it is clear from these two passages in comparison with the deliverances from demons accomplished by our Lord and His apostles that what counts are the spiritual gifts and divine power behind them, not any special knowledge or “magic” formula. All indications are that the ability to cast out demons was, along with healing and tongues and etc., one of the spectacular transitional gifts that are no longer being given (see the link: “Is speaking in tongues biblical?”). It seems that the "authority" to do this is of a special type that had to come directly from our Lord to His apostles (cf. Lk.9:1 - there is no recorded "gift" of exorcism). For more on demon possession in general please see following links:
Part 4 of the Satanic Rebellion series, section V.4: “Demon Possession”
Spiritual Warfare II
Satan, his Demons, and the Gnostics
Antichrist: Alive and Well and Living on Planet Earth?
To return briefly to the case of Mark 5:7, it certainly shows the spiritual hardness and hypocrisy of the fallen angel followers of the devil, who have been in rebellion from God since before the beginning of human history: now they want Him to "make Jesus play by the rules as they see them" on the one hand, and fail even yet to understand that the Father has a higher opinion of the Son than of them! This furnishes a fine perspective for the hardness that comes to human beings too when truth is rejected once and for all, like criminals who have no compassion whatsoever for their victims or true remorse for their crimes, but mourn deeply for their own personal set-backs.
As to the water that those who ate the fish and bread miraculously multiplied by our Lord must have drunk, you are right that scripture is silent about this. While it is true that Jesus is the "Rock" from which the Israelites drank water divinely provided in their time of need (1Cor.10:4), and that water generally is symbolic of the Word of God (i.e., the divine provision of truth from our Lord Jesus who is the Truth; cf. Jn.3:5; Eph.5:26, etc.), I am nevertheless inclined to think that we would be given some indication if that were miraculously provided too, especially since Jesus quizzes His disciples about these event later and only asks about the food (Mk.8:20). It is likely that both miraculous feedings took place near the Sea of Galilee (or some other water supply), and it is probable that there was water in the nearby streams in any case (since they sit down in green grass; i.e., it is not the dry season: Mk.6:39).
In our Lord.