Complex sentence: One who studies swimming in all its forms is called a nektologist.we have organisms whose initial part of their lifes are spent as plankton but when they grow and increase in body size they become nekton.
Split into simpler sentences: One who studies swimming in all its forms is called a nektologist. There are organisms whose initial part of their lives are spent as plankton but when they grow and increase in body size they become nekton.