And as he was passing alongside the Sea of Galilee, he saw Simon and Andrew (the brother of Simon) casting a net into the lake,a for they were fishermen. Bible other translations
The Sea of Galilee is a lake.

“the lake.” The “Sea of Galilee” is a lake, about 7.5 miles wide (12 km) and 13 miles (21 km) long (the size can vary somewhat as the water level rises and falls). A person can stand on the cliffs on either the east or west side and see the entire lake very easily.

Commentary for: Mark 1:16