【go to the bottom】 —(of ships) sink:

• The men were all sick, and the women and children thought they were going to the bottom.

【touch bottom】 —(also: hit bottom)

1. (of prices, sales, etc.) reach the lowest or worst point:

• Prices touched bottom during the depression years.

2. (of people) become extremely poor:

• Until they 【touch bottom】 , it is difficult for people to get financial help.

Note: The expression is but partially antonymous in meaning to the phrase go through the roof—(also: hit the roof )

1. (of prices, sales, etc.) increase very rapidly; surpass the expected limit:

• We got here before prices went through the roof, so we were able to get a nice house at a great price.

2. show extreme anger about smth.:

• There is just one problem: Oscar will go through the roof when he hears about the project.