If you're looking for a meeting place or a good stop around ½ or halfway between Ocean City, FL and Navarre, you can try Harris, FL, which is about 14 minutes west of Ocean City, FL, or about 14 minutes east of Navarre.
About ¼ or a fourth of the way, you can stop at Mary Esther, FL. This is about 7 minutes southwest of Ocean City, FL.
About ⅔ or two thirds of the way, you can stop at Wynnehaven Beach, FL. This is about 17 minutes west of Ocean City, FL, or about 10 minutes east of Navarre.
If you drive straight through without stopping at all, the total distance is 17 miles. The distances shown above don't include local roads to get into each town, so if you're planning a long road trip, make sure you factor in traffic and road conditions, rest stop breaks, and interesting detours along the way. If you're in a rush, you can do the trip with zero stops, and your total travel time would be around 28 minutes.