It recalls your memory of tranquil streamlet, winding smoothly through a green grassland covered by pleasing trees till entering the sea; but the sea is so peaceful, so silent, and so indifferent that you are suddenly bothered by a vague anxiety.
It makes you think of a serene creek that meanders gently through a green grassland and that is in the shadows of pleasant trees, until it finally flows into the ocean, but the ocean is so calm, so soundless, so indifferent, that suddenly you are puzzled by a fuzzy uneaseness.
它让你想起宁静的小溪，蜿蜒平缓地流过绿色草原，被赏心悦目的树木遮蔽着，直至最后流入辽阔的大海；但大海如此平静，如此无声，如此无动于衷，以至于你突然间被一种模糊的不安所困扰。（from The Moon and Sixpence)
It reminds you of a tranquil stream，winding around the green prairie，covered by delightful trees，until merging into wide-open sea. However, the sea is so quiet, so silent, so indifferent, that you are annoyed by a vague uneasiness all of a sudden.
It reminded you of the tranquil creek, winding through the green meadow smoothly, hidden in the cheerful woods and in one end , merged into the extensive ocean; While the ocean was so calm, so quite, and so unemotional that suddenly you felt disturbed by a vague anexiety.
【汉译英 From Chinese to English】
它让你想起宁静的小溪，蜿蜒平缓地流过绿色草原，被赏心悦目的树木遮蔽着，直至最后流入辽阔的大海；但大海如此平静，如此无声，如此无动于衷，以至于你突然间被一种模糊的不安所困扰。（from The Moon and Sixpence)
It recalls your memory of tranquil streamlet, winding smoothly through a green grassland covered by pleasing trees till entering the sea; but the sea is so peaceful, so silent, and so indifferent that you are suddenly bothered by a vague anxiety.
它让你想起宁静的小溪，蜿蜒平缓地流过绿色草原，被赏心悦目的树木遮蔽着，直至最后流入辽阔的大海；但大海如此平静，如此无声，如此无动于衷，以至于你突然间被一种模糊的不安所困扰。
It makes you think of a serene creek that meanders gently through a green grassland and that is in the shadows of pleasant trees, until it finally flows into the ocean, but the ocean is so calm, so soundless, so indifferent, that suddenly you are puzzled by a fuzzy uneaseness.
这里可能用sea更合适，“seas are smaller than oceans and are usually located where the land and ocean meet”，ocean通常就是五大洋。
有个typo: uneasiness
其他的都很好，结构语感都非常好！
【汉译英 From Chinese to English】
它让你想起宁静的小溪，蜿蜒平缓地流过绿色草原，被赏心悦目的树木遮蔽着，直至最后流入辽阔的大海；但大海如此平静，如此无声，如此无动于衷，以至于你突然间被一种模糊的不安所困扰。（from The Moon and Sixpence)
It reminds you of a tranquil stream，winding around the green prairie，covered by delightful trees，until merging into wide-open sea. However, the sea is so quiet, so silent, so indifferent, that you are annoyed by a vague uneasiness all of a sudden.
wide -open sea译得好。原文就是用分号的，这样才是一句话翻译：）
It reminded you of the tranquil creek, winding through the green meadow smoothly, hidden in the cheerful woods and in one end , merged into the extensive ocean; While the ocean was so calm, so quite, and so unemotional that suddenly you felt disturbed by a vague anexiety.
白云mm是第二个把海议成“ocean“的，我查了查：
seas are smaller than oceans and are usually located where the land and ocean meet.
Ocean可能更多时候是我们通常所说的五大洋，这里可能sea更好些，因为它与草原比邻。
还有就是分号后面可以直接小写。