Fast 40 yards sprint time?

Hi! I'm a swimmer and I have no idea what a fast running time is. I spend most of my time in the pool so I guess i don't have time to check these kind of events out. Anyway at dryland today after swim practice we did some 40 yard sprints and I was running way faster than my other teammates....After about 6 sprints and a couple suicide sprints I asked my coach to time me. I went a 4.9....Is that good??? Thanks )