Buy RS3 Blue blubber jellyfish
The blue blubber jellyfish is a top food choice in RuneScape 3. It is eaten in 3 bites, and each bite heals 750 life points. That means one jellyfish can heal 2250 life points in total. Eating it does not lower your adrenaline, and it does not share a cooldown with many other foods and potions. This makes it great for hard bosses and long fights.
You can boost its healing even more. Expensive spices add 50 life points per bite, and the necklace of gluttony adds 100 per bite.
Catching and cooking these jellyfish takes a lot of work. They are only found at the Deep Sea Fishing Hub and need level 91 Fishing to catch. Cooking them needs level 95 Cooking, and they can still burn until high levels even with cooking gauntlets. Buying them ready to eat saves all that time.
Partially eaten jellyfish can be decanted with the clan representative at War's Retreat, Granny Rowan at Fort Forinthry, or Jellyfish Mender Judd at the Deep Sea Fishing Hub. Stock up on blue blubber jellyfish and keep your life points high in any fight.