To stay afloat means to float on water without sinking. A boat stays afloat when it's designed well and not taking on water. When you're swimming, you stay afloat by moving your arms and legs or by floating on your back. Sailors whose ships have sunk might cling to floating debris to keep themselves afloat until rescue arrives.

The word also describes keeping something going despite difficulties. A business stays afloat when it earns enough money to pay its bills and keep operating, even during tough times. A struggling student might work hard to stay afloat in a challenging class, doing whatever it takes to keep from falling behind. When your family keeps a project afloat, you're managing to continue it despite obstacles or setbacks.

The core idea in both meanings is staying above the surface, whether that's literal water or the metaphorical waters of challenge and difficulty. Something that's afloat hasn't gone under.