keep a sharp lookout

The parent must constantly keep a sharp lookout.

It will seek light emitted by the first stars and galaxies close to 14 billion years ago, and keep a sharp lookout for possible signs of life.

On March 18, Turkey advised ships to keep a “sharp lookout” and report any possible mines that had drifted from Ukrainian ports.

An’ if he didn’t, well, we’d keep a sharp lookout anyhow.

Feet splayed for balance in the Caribbean swells, I shaded my eyes to keep a sharp lookout for any coral reef in our path — a hazard to the catamaran we’d chartered for a week.