Size & Type: Large Magical Beast (Aquatic)
Space/Reach: 10'/20'
HD: 9, 18 Huge
Speed: Swim 20'
Ability Scores: Str +8, Dex -2, Con +8, Int -2, Wis -2, Cha -2 - Net +8, four penalties
Natural Armor: 0
Natural Weapons: One Primary Touch (1d10 acid, plus Con-based Fort or 2d4 Dex)
Skill List: Listen, Spot, Swim
Body Shape: Jellyfish
Speech (Languages): No
CR: 7
WotC LA: -
Our LA: -0
First thing: They aren't devils. Second thing: The Devil Sail has more RHD than AC. Zero natural armor.
So it can Improved Grab a creature at least one size category smaller than it, and it has a few PLAs. 3/day Dimension Slide and Painful Touch at ML 11, in addition to the attack/defense modes we can never figure out how to convert.
Finally, its Underwater Sense lets it detect any creature within 60' while under water. Though it's less effective at detecting creatures without nervous systems, like undead, oozes, and constructs. Such creatures can only be detected from 30' away. Figments never fool a Devil Sail under water, and there's no mention of that only being ones within range.
Yes, that's it. See you guys tomorrow.