You are right about those big custom builds not being publicly advertised. Most of those projects start long before the owner ever sends an RFI to a traditional lead board. If you want to get on the radar for the high-end stuff with the complex rooflines and multiple bays, you have to stop looking for general contractor leads and start targeting the designers and specialized consultants who are handling the initial design package. These projects aren't usally looking for a general carpenter; they're looking for a specific partner who can handle the detailed scope of work they've specified. So, instead of cold calling builders, start reaching out to the architectural firms in the coastal area and the interior designers who specialize in those luxury builds. They are the ones drafting the plans and specifying the level of detail required for the custom framing and finish. Once they trust you with one of thier detailed drawings, they will bring you back for every subsequent phase of the project.
Another critical connection you shold be building is with niche subcontractors. Think high-end structural steel companies, specialized glazing fabricators for those unique window shapes, or complex roofing systems vendors. These guys are always working on the most elaborate homes. If they are alredy specifying their work on a site, they know exactly who the reliable carpenter is to follow through on the structural elements. Getting recommended by a highly specialized sub carries a lot of weight and gives you a direct line to the project before the GC even puts out the call.
And even more niche but effective, connect with the builders' lenders or the escrow officers who handle the financing for these large waterfront properties. They are the ones who vet the entire project team and they often keep a list of vetted, high-quality tradespeople who they trust for the build. That's how a lot of these custom contracts are funneled. It is about building relationships with the people who are acutally in the room when the complex plans are being drawn, not the people who are advertising work.