How does the symbol of water in The Bell Jar represent the protagonist's descent into insanity?

In The Bell Jar by Sylvia Plath, Esther Greenwood experiences events which will change her life significantly. However, rather than giving Esther insight, the events eventually lead her towards a state of madness. Womanhood and all the expectations and conventions associated with it, prevent Esther from progressing and, despite surviving a suicide attempt and being "retreaded and approved for the road," she seems interminably trapped in her own version of a bell jar, "stewing in my own sour air."  

Esther is confused about what wholesomeness really is and constantly seeks to purify herself- even viewing vodka - which, of course, looks clear like water, in the mistaken belief that it will cleanse her spiritually. Soaking in a hot bath also has Esther hoping for a spiritual cleansing,as she feels herself "growing pure again." Therefore water contributes to the reader's understanding of Esther's confusion and her search for concrete ways to satisfy her abstract misconceptions. Water becomes as much an oppressive symbol for Esther as everything else. She even considers not washing in an attempt to separate herself from her reality- rejecting her physical body which she sees as being capable of plotting against her. She fights her body with "whatever sense I had left, or it would trap me in its stupid cage.” When trying to drown herself, her body fights back and reveals her subconscious feelings and her desire to live, although she will keep fighting it, increasing her paranoia. 

Esther increasingly becomes less and less trustful, even comparing words themselves to " sea-polished pebbles," and her suggestion is that they can change in an instant into something they are not. Water, for Esther, holds mysteries and contradictions that only serve to add to her confusion. Sometimes it gives her closure, such as when it rains at her father's grave and she cries - "howled"- over her loss but then it also adds to her pain.   

Esther has been contemplating the best ways to kill herself, slashing her leg as a test. Concerned that it might not work, she has also tried hanging herself unsuccessfully, and even sits on the beach and wonders about drowning, rationalizing about how best to merge everything that is terrible and everything that could be good about her life. In the water, she is unable to drown herself and later makes her attempt to kill herself by taking her mother's pills, which event is the path to her recovery. 

How does the symbol of blood in The Bell Jar represent the protagonist's descent into insanity?

When Esther bleeds, the blood marks major points in her life.

In Chapter 9, Esther meets Marco, whom she terms "a woman-hater." She describes him as like a god: "invulnerable and chock-full of power." Marco proves her correct as he later throws her to the ground to rape her, but Esther resists, kicking him and punching him in the nose. When his nose bleeds, Marco smears this blood on her cheeks, staining them as he demands his diamond pin which she put into her handbag. After she returns, Esther throws her clothes, one by one, off the building. In Chapter 10, she writes, "The face in the mirror looked like a sick Indian." The transformation has involved suffering, and she leaves the blood on her face as she takes the train back home.

Then, in Chapter 12, after her mother has taken her to Dr. Gordon, a psychiatrist, Esther is recommended for shock treatments. As her mother talks, Esther reads of a man's suicide. Later, she walks through a public park, looking at the Japanese Weeping Scholar tree, reflecting upon how the Japanese "understood things of the spirit": They disemboweled themselves when anything went wrong." Thinking that it must take great courage to stick knives into oneself took much courage, Esther remarks that her only trouble with that is she hates the sight of blood. Nevertheless, she decides to "open her veins" in the tub like one of the ancient Romans, but she cannot do it. So, she decides to cut herself for practice by letting the razor drop to her crossed leg.

I thought of getting into the tub then, but I realized my dallying had used up the better part of the morning, and that my mother would probably come home and find me before I was done.

This episode suggests her depression and her wish to sacrifice her body to end her mental torture.

In Chapter 19, having being fitted with a diaphragm because she wants to rid herself of her virginity as she feels it is a burden that she has had to defend, she seeks a sexual partner. She meets Irwin, a math professor, goes to his apartment for coffee, and decides to seduce him. Her sexual experience is painful, and Esther bleeds quite a bit, wondering if she is still a virgin.

It occurred to me that the blood was my answer....I smiled into the dark. I felt part of a great tradition.

However, Esther continues to bleed and begin hemorrhaging and has to be taken to the hospital. Rather than having been pleasurable, Esther's sexual experience has been more like ritual sacrifice. For, she has sacrificed her virginity for a peace of mind that she does not attain.

What motifs and symbols show the protagonist's descent into insanity in The Bell Jar?

The Bell Jar reveals the conflicts that haunt Sylvia Plath in her own life as her protagonist, Esther, struggles with her own fears and anxiety, unable to motivate herself even though she knows that,

"I should have been excited, the way most of the other girls were, but I couldn’t get myself to react. I felt very still and very empty…moving dully along."

Esther sees life in extremes where there is rarely a middle ground. As a woman, she may be either a virgin or a whore but, whichever she is, she must serve men's purposes, not her own. Esther recognizes her own isolation, and exists along a "white, broad, infinitely desolate avenue." She even compares life to living under a bell jar where "the world itself is the bad dream." Even if Esther is aware of her unstable position and that she is "stewing in my own sour air," she seems unable to prevent what becomes inevitable - madness.    

She feels trapped and unable to make sound decisions as, either way, she can never be fulfilled but only satisfy men's needs. This understanding contributes to Esther's insanity because, psychologically, she suffers constant disappointment and distress. Despite the various role-models and female characters which Esther could emulate, she always finds herself lacking. 

Esther almost watches her life unfold through the mirror images that she, sometimes, does not even recognize as herself. This contributes to her descent into insanity as she cannot understand nor explain herself. When Esther talks about the fig tree and the potential for "a wonderful future,' she imagines herself "sitting in the crotch of this fig-tree, starving to death." By making choices, she must exclude other choices and thus cannot make satisfactory decisions:"The figs...one by one, (they) plopped to the ground at my feet."

All Esther's experiences are painful; never joyful. Hence the blood motif is particularly strong. Esther must suffer at the hands of Marco; she considers killing herself by slashing her leg and wondering if she could actually kill herself and not fail; she needs medical attention when she loses her virginity; all of these events have the potential to be teach Esther something but, for Esther they simply increase her fear of life and, consequently of death. She cannot see herself the way others see her and does not even recognize her own attempts to save herself, rather picturing her body as something to fight against.