The Vibe Beach Club –
Royal Caribbean does have a pool deck section with adults only 16+, with 2 hot tubs, 1 pool, a bar, and plenty of pool loungers that is free of charge, but loungers do fill up quickly. There are a few open floors, without a pool nearby, where you can layout and sunbathe, but it is often windy, hot, and crowded.
Norwegian has a private place with a capacity of around 100 guests in their Vibe Beach Club, fellow Vibe veterans will probably be mad that I’m sharing this hidden gem as it isn’t publicized much, but you can purchase a pass on day one for around $125-150 a person, and have access all week. Padded loungers, misters, hot tub, umbrellas, bar, snacks with usually only a dozen or so other cruisers using it at the same time as you.