This could be in a physical sense. This could mean that they have self harmed or have started the process of suicide. This could also be mentally. This could mean they are blaming themselves for letting their mental illness consume them. The speaker then says “and the sun has gone; (3)” They feel there is no hope for them to get better.
Next the speaker describes a physical feeling. In the second stanza that consists of lines 4, 5, and 6, the speaker writes “the hung weight of my legs (4) a plumb-line, (5) my fingers raw, my arms lead; (6)” This is describing their physical state as their mental illness drains the life from them. The speaker uses a metaphor, comparing their arms to lead to emphasize the heaviness they are feeling..
In the third stanza, the speaker states “the currents pull like weed (7) and I am very tired (8) and cold, and moving out to sea. (9)” This stanza describes the speaker coming to find acceptance with how their life is ending. Line 7 suggests that the speaker is nearing their death. Line 8 and 9 suggest that he does not want to struggle but rather just accept what he has