How did naval ballistics work in world war i?

There weren't many significant naval engagements in WWI, but in those that did happen many of the vessels were miles apart, moving at 20-30 knots in rough seas/weather, with no assistance from radar. If you're 10 miles apart, the curvature of the earth plays a roll, you're swaying up and down, and both vessels are moving quickly. Seems a darn near impossible task. How would gunners have calculated shell trajectories?