To keep your head above water means to just be able to manage, especially when you have financial difficulties.

For example:

The business is in trouble, but we’re keeping our heads above water.

We all have to cooperate just to keep our heads above water.

Keeping your head above water in difficult situations can be considered a virtue.

With a part-time job, I was able to keep my head above water.

We have so many orders that we can hardly keep our heads above water.

Tradução: evitar afundar em três sentidos principais: afundar na água, literalmente; afundar no sentido de ir à falência; afundar no sentido de não conseguir realizar todas as tarefas que se tem.