Please avoid incomplete sentences (aka sentence fragments).
If you were to ask me tomorrow, couldn’t tell you my answer.
The water clear and chilling as I swam stroke after stroke underwater.
Sometimes authors purposely use sentence fragments. The following sentence is from George Orwell’s Homage to Catalonia. Here Orwell uses an incomplete sentence to produce an effect of immediacy or informality. Be sparing in your own such use.
“In the Lenin Barracks in Barcelona, the day before I joined the militia, saw an Italian militiaman standing in front of the officers’ table.”
Sentences in Green are incorrect.