Retailer's overheads, IMO, mitigate against a tiny niche market such as this.
boats and cars do seem a natural fit,but remember the yachtie scene is now fashion-driven, highly fragmented manufacturer-sources and huge ranges....A copy of Practical Boat Owner / Yachts and Yachting / Yachting World will show the enormous stockholding and advertising needed to be a player.
You'd maybe better considering an ultra-specialised market (balloonist's requirements? )
On-line is a given for almost any major purchase,As some mentioned, physical stores become a showroom for punters to see and feel before buying cheaper online.
Retail only seems to work for the very highly specialised and at the other extreme "loose change" impulse-buys.
As an aside , I once investigated shoes and brasierres (old -fashioned, I know)
but although both are necessities (women need at least 3 bras and they have limited -life and a decent ticket-price AKA unit sale )
both types of merchandise suffer the same problem....a huge variety of sizes in each style, PLUS colour variations....the stock-holding is GINORMOUS.
Not saying you can't make a profit, but it would be a very steep learning-curve and need a lot of luck.....apart from that, the competition is already established and has already made the mistakes.
let the shop, draw the rent.....unless you are a gambler and need a challenge.