Couple of things come to mind. We have friends at our dock who use either the stick-on LED pucks, or those strips. I actually used them for TV backlighting at my house.

In my case, I really wanted to stick with a stock look, and positioning for my cockpit lighting. I only have 6 fixtures up there. 2 in the arch and 4 low, and we always have transient boaters come up to us at night asking about them. The one thing I give up, however, is the almost infinite control over color, color changing, music interaction, etc. These are only 4-color, non-dimming, but they still use the factory switches, and mounting points.

Red - arch and low

Purple - low only

Blue - low only

Still, if I had a boat that didn't already have the existing courtesy lights, I'd consider leaning towards the better quality strips that are already waterproofed, but use a better adhesive.

With regards to underwater lighting, I'd tend to stick with known quality brands. I used Lumitec for all of my courtesy and underwater stuff, and the quality is second to none.

It's good side work, and word travels fast if you're good at what you do, keep things neat and clean, and are good with systems integration.

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look up lumitech prices...underwater lights are silllly money (1 light is $500)...you can definitely buy the shitty amazon versions and do it 20 times yourself before you spend what you should the first time. no dealer/mechanic will install trash because its just gonna break and you're gonna bitch(maybe not you specifically but they've all learned its not worth it) about how you paid 500 to have it installed and it should work. blah blah....look up bennington....they just use waterproof roll led kits inside the edge railing. it shines down on the toobs nice. More on reddit.com