Someone or something try to snatch sheep out of Jesus' hand because they do not believe in Jesus and the very works that He is doing, so they try to bring disblieves amonge those who believes and are sheep in Jesus' hand.  Satan the devil and his agents are trying.

If you are a child of God, rooted in faith and believe in Jesus, no one can snatch you from Jesus, hand. 

The Holy Spirit is like rivers of living water because as a believer, each time you yourn for it (the Holy Spirit), it quenchines your spirit it gives you understanding into the truth of the word of God.

As Jesus said "If anyone is thirsty, let him come to me and drink! He who believes in me, as the Scripture has said, from within him will flow rivers of living water." that thirst is of the word of God.