To understand the history and development of the Mark 3 , you need to know some history about the Everglades Challenge. The Core Sound series of boats have been competing successfully for almost 10 years in the annual Watertribe Everglades Challenge. This 300 mile distance race from Tampa Bay to Key Largo, Florida is open to all boat types and typically has over 100 entrants. Kayaks and small sailboats make up the majority of the entries and all boats must be able to push off from above the high tide mark which is intended to limit the entries to small trailer-able crafts. From 2006-2009, the race was won by Graham Byrnes in class 4 (sailboats) fist in a Core Sound 17 'Green Heron' and later in the EC-22 'Southern Skimmer' . Since then it is a common sight to find B&B designed sailboats in the lineup. In 2013, Paul and Alan Stewart in their Core Sound 20 'Dawn Patrol' set a course record with a time of 2 days and 2 minutes followed closely that year by a new Core Sound 17 'La Perla' sailed by Phil Garland and Dan Neri. In 2018, Paul and Alan beat their previous record by 5 minutes finishing just under the 2 day mark. They still hold the record for a 20' monohull in the race.

The success of Southern Skimmer and Dawn Patrol can be partly attributed to their cuddy cabins allowing the sailors a safe haven from the wind and spray to rest between watches. Paul and Alan retrofitted their Core Sound 20 with its cabin during the build but there were no plans available and it was a one off design modification. An attempt to copy the shapely cabin on Graham's EC-22.

As followers and entrants of the Everglades Challenge began to take note of the Core Sound's success, more and more requests were made for a boat with a small cabin similar to the EC-22 and Dawn Patrol. In 2013 Chick Ludwig, long time friend and builder of many B&B boats (like the first OB-20 'Princess'), officially requested the design and kit for a new Core Sound 20 with a cabin! Now discontinued, this boat was called the Core Sound 20 Mark 2 and featured a cuddy cabin, raised cockpit seating, water ballast, and a self draining cockpit. Click here to watch a video of the Mark 2 proving her self righting capability. This boat was later campaigned successfully in the Watertribe North Carolina Challenge by Julie and Frank Miguel. More pictures and video on his blog.

Graham saw room for further improvement in the Mark 2 and very soon after the Core Sound 20 "mark 3" (hence the name) was drawn and hull #1 was built by former Core Sound 20 builder/owner and watertribe racer Doug Cameron. His blog has more pictures of construction and sailing videos.