There are other uses. It can mean to sink (hundirse), and to auction (subastar) something.
A business can go under (irse a pique), that is, into liquidation (liquidación). Many businesses are going under as a result of the Covid 19 virus restrictions.
- The bank went under after the crash (… se hundió despues del crac).
- Ricardo´s Ferrari will “go under the hammer” this month (…será puesto en subasta…)
- The ship is going under (está a punto de hundirse), or the ship is sinking.
There is a medical use (informal). If someone “is going under the knife” tomorrow, it means that he is going to have a hospital operation (intervención).