You can get these on eBay. You can run these all the way down your boat. The 5050 leds are plenty bright. You can also cut to length in 3 led intervals if you want shorter ( requires soldering). If you use the whole strip, you will need to power from both ends of strip. If you don’t, one end will be bright and it will get dim at the other end.
https://m.ebay.com/itm/Wholesale16ft...from=R40&rt=nc