cruise · 3 tiers tracked · 1 free way in, 0 conditional
Most cruise status comes only from stacking nights on board; Celebrity's Elite tier has a shortcut that skips the ships entirely. If you're Diamond in Royal Caribbean Crown & Anchor, you already qualify for Celebrity Elite — the two brands sit under the same parent company and match tier-for-tier automatically. You enroll through Celebrity's own site or app, there's no fee, and the match stays in place going forward rather than expiring after one cruise.
That's the only route in: Elite Plus and Zenith aren't reachable this way, so if you're aiming higher than Elite, you're earning those tiers through Captain's Club sailings rather than a match.