A "dragnet" can take various forms, from a rectangular net that's equipped with floats on top and weights at the bottom for "dragging a river," to a cone-shaped net that's "dragged" through the sea. Although their designs may be different, their purpose is not - to catch everything that cannot fit though the size of their mesh.
"The kingdom of heaven is like unto a net"
At least four of the twelve apostles were fishermen who the Christ called to become "fishers of men":
"From that time Jesus began to preach [The Messiah's public ministry began as John the Baptist's ministry was ending, see John's Last Days], and to say, Repent: for the kingdom of heaven is at hand."
"And Jesus, walking by The Sea Of Galilee, saw two brethren, Simon called Peter, and Andrew his brother, casting a net into the sea: for they were fishers. And He saith unto them, Follow Me, and I will make you fishers of men. And they straightway left their nets, and followed Him."
"And going on from thence, He saw other two brethren, James the son of Zebedee, and John his brother [see also Do A Little Favor For Your Cousins?], in a ship with Zebedee their father, mending their nets; and He called them. And they immediately left the ship and their father, and followed Him." (Matthew 4:17-22 KJV)
Jesus Christ used a fisherman's dragnet as an analogy for the Judgment Day that awaits everyone (see When Will You Be Judged?):
"Again, the kingdom of heaven is like unto a net, that was cast into the sea, and gathered of every kind: Which, when it was full, they drew to shore, and sat down, and gathered the good into vessels, but cast the bad away."
"So shall it be at The End Of The World: the angels shall come forth, and sever the wicked from among the just, And shall cast them into the furnace of fire: there shall be wailing and gnashing of teeth." (Matthew 13:47-49 KJV)
Fact Finder: What did the Christ mean by the term "fishers of men"?
See Fishers Of Men