In the New Testament, Gennesaret (from the Greek word that was derived from the Hebrew word for harp) was the name used for a town in Galilee that was located (it no longer exists) on the western shore of the lake that was also known as Gennesaret (thereby implying that either the lake was named after the town, or, more likely, the town was named after the harp-shaped lake), a lake more popularly known from the region i.e. the Sea of Galilee.
In the Old Testament era, the town was known as Chinnereth which means harp-shaped, another apparent reference to the sea, or lake, of Galilee. The wholly-surrounded by land fresh-water Sea of Galilee is, technically, actually a lake i.e. a sea is "a division of an ocean or a large body of salt water partially enclosed by land" whereas a lake is "a body of (usually) fresh water surrounded by land."
"And when they were gone over, they came into the land of Gennesaret"
In the Old Testament era, "Chinnereth" was used for both the town and the lake:
"the border shall descend, and shall reach unto the side of the sea of Chinnereth eastward" (Numbers 34:11 KJV)
"And the fenced cities are Ziddim, Zer, and Hammath, Rakkath, and Chinnereth" (Joshua 19:35 KJV)
After one of the most famous events of the Scriptures, the miraculous walking on the water by Jesus Christ, and Peter, they landed at Gennesaret where the miracles continued.
"And straightway Jesus constrained His disciples [see Disciples and Apostles] to get into a ship, and to go before Him unto the other side, while He sent the multitudes away. And when He had sent the multitudes away, He went up into a mountain apart to pray: and when the evening was come, He was there alone. But the ship was now in the midst of the sea, tossed with waves: for the wind was contrary."
"And in the fourth watch of the night Jesus went unto them, walking on the sea. And when the disciples saw Him walking on the sea, they were troubled, saying, It is a spirit; and they cried out for fear."
"But straightway Jesus spake unto them, saying, Be of good cheer; it is I; be not afraid."
"And Peter [see also Peter's Ministry] answered Him and said, Lord, if it be Thou, bid me come unto Thee on the water."
"And He said, Come."
And when Peter was come down out of the ship, he walked on the water, to go to Jesus. But when he saw the wind boisterous, he was afraid; and beginning to sink, he cried, saying, Lord, save me."
"And immediately Jesus stretched forth His hand, and caught him, and said unto him, O thou of little faith, wherefore didst thou doubt?"
"And when they were come into the ship, the wind ceased. Then they that were in the ship came and worshipped Him, saying, Of a truth Thou art the Son of God."
"And when they were gone over, they came into the land of Gennesaret. And when the men of that place had knowledge of Him, they sent out into all that country round about, and brought unto Him all that were diseased; And besought Him that they might only touch the hem of His garment: and as many as touched were made perfectly whole." (Matthew 14:22-36 KJV)
Fact Finder: What was the town on the coast of the Sea of Galilee in which Jesus Christ went to live after He left Nazareth?