I'll not address resolving coastline since that's an already known problem and currently has no solution. For shallow sea discovery, radar is good enough to ge

I'll not address resolving coastline since that's an already known problem and currently has no solution. For shallow sea discovery, radar is good enough to get a detailed map of terrain and medium to large scale objects. There is also a heuristic that can be applied in finding whether something is man made or occurs organically. Software applying this heuristic was used to debunk suggested "alien" structures on Mars. This same approach can be used to scan and find potential settlements underwater for excavation. At the very least some follow up core drilling. The only sales pitch needed is one that gets the money to buy some equipment, pay a few people to sit a long time in a boat trolling, and maybe longer at a desk organizing and publishing the data. None of this is magical, requires magical thinking, or magical amounts of money. The issue is convincing enough people its worth at least trying to find new or more evidence.