A ring buoy (life preserver) added in 2020 (Unicode 13.0) specifically to round out water-safety emoji — it's used literally for boating/swimming safety posts, but online it's picked up as a metaphor for 'someone throw me a lifeline,' i.e., help during a rough time. Its round shape with the red cross-bands makes it instantly readable even at tiny sizes.
Keywords: buoy, float, life, lifesaver, preserver, rescue, ring, safety, save, saver, swim