bob up

1. Literally, to move up into view above the surface of something. Otters often bob up in this part of the harbor, so it's a great place to take photographs. I know you thought it would be cool to have colored ice cubes, but every time the red one bobs up in my drink, it's a bit jarring. We held hands, breathless, panicked, waiting for the girl to bob up from under the water.

2. To appear, arise, or come into being quickly or unexpectedly. We thought the meeting was over until several questions bobbed up from the back row. The city is deceptively small, and acquaintances often bob up at the most unexpected places. When you're planning an event, there are always problems that bob up at the last minute.

bob up

Appear suddenly or unexpectedly. For example, I didn't know anyone in the group until Harry bobbed up. This term uses the verb bob in the sense of "to bounce," a usage dating from Chaucer's day. [Late 1800s]

bob up

To come to the surface quickly, especially after being underneath for a short time: I didn't think anyone else was swimming in the pond, but then someone's head bobbed up right in front of me.