Sonar is used in everything from fishing to submarines plus there is a class of boats called sonar which are used in sailboat races and recreation. I mean if I need car parts, I type it in and usually the first site that shows up is carparts.com and I'm thinking the same here. I just need an honest appraisal and damnit, don't tell me just the reg fee. Here's a link to the boats: shumwaymarine.com
it has great relevance to companies manufacturing sonars but the only problem is that their target audience is very restricted and having such a domain would do them no good according to me... they are known for brand names its not some candy kind of business that every other person will be interested in