bob up

In the 30 years before the mid 1990s, net migration, the number arriving minus the number leaving, bobbed up and down but was broadly balanced.

He beamed as his head bobbed up and down.

I reassured her this was not the case and rapidly tried to build a bond as we bobbed up and down a few metres apart.

A standout moment on Tamara's nine-week expedition in Antarctica's Weddell Sea was when two seals bobbed up to the surface to take a deeper breath after falling asleep alongside the ship.

He disappeared under the water and in a while his head bobbed up, far out and downstream.