|Crateria Kihunter Room||Adjacent rooms||West Ocean|
Sweetnumb made an image album detailing how to get the HBJ for the moat.
Twocat also has this video describing some of the nuances:
If you're doing the two-spark method, as opposed to Ocean Fly, you can Stop on a Dime to nudge your way back towards the ledge, then do a 1-tap or 2-tap through the door transition to charge the next spark.
Most runners will instead run through the door, then do a tighter 2-tap entirely within West Ocean.
If you're doing the Early Grapple route, it's faster to just Grapple across the Moat instead of sparking.
If you have Spring Ball, you can mid-air morph, bounce off of the missile platform, and land on the other side. It is technically possible to do this with Hi-Jump Boots, but significantly harder, so you'll likely want to turn them off before attempting this.
If you fall on the far side of the missile platform without Gravity Suit, or Morph Ball and bombs, you will be softlocked.