My experience from trying to sell to the freediving market: don't bother, you will lose money, no matter how good your idea is. Freedivers are among the cheapest of all consumers, they expect something for nothing. Most freedivers will not even use a new piece of gear, if you give it to them for free.
Try to adapt your invention to another market.
Nevertheless, if you use the example of fluid goggles, which I originally brought to market in 1998, you could say this was a 'good idea' and someone might want to copy it. It was never patented in any way, and it probably could not have been, as there were weak attempts at this idea in the 1980's (of which I was unaware when I 'invented' them).
I sold the goggles from 1998 until now (2007), and during this period, one company DiveFree, brought out a competitor goggle for a period of around 6 months. They thought that they would enter the 'lucrative' fluid goggle market, only to realize that sales were extremely poor. In fact, they had stolen a good market share, but there was little or no market to start off with. They were so disappointed with sales that they realized it was never worth their time, so they stopped making the product. I continued selling goggles, even though it has never been worth it-- I do it more like a service to the community, and during long periods the goggles are out of stock when I don't have the motivation to make more.
When I entered the freediving computer market with the F1 in 2005, the true colors of the freediving consumer market came to light. There could be no denying reality after a competition in Hawaii in 2006, when the F1 was offered as the official gauge. Only one competitor would wear the computer. The others said it was too bulky and ugly, even though it was barely larger than a D3, and much small than a Mares Apneist which had been the staple computer of the community for years. When you can't even give something away for free, it is time to look for a new market, which is what I did, and what you should do too.