You may know that the manta ray rings have a bug that causes their actual hitboxes to differ from their graphical appearances. This video uses a hack that displays the manta ray rings as Mario actually experiences them. Thanks to nim ( /channel/UCG_b-lywDked3HfbZQXU8Gw ) for the patch.
This star is different from other DDD stars in that it's not fastest to build up B swimming speed. Mario can get the rings and star quickly enough that the extra time spent to get speed isn't worthwhile. This star was also optimized using automated optimization tools.