This is the 5088th most frequent Russian word.
морскую
The Russian word "морскую" is the accusative singular feminine form of "морской," meaning "marine," "naval," or "sea-related."
In this sentence, 'морскую' is an adjective modifying 'жизнь,' meaning 'marine' in relation to life.
Я люблю морскую жизнь.
I love marine life.
Here, 'морскую' defines 'черепаху,' specifying it as 'marine' or associated with the sea.
Мы видели морскую черепаху.
We saw a marine turtle.
In this example, 'морскую' describes 'биологию,' indicating the field of biology that deals with the sea.