Gyarados

A habitat matching this ambience raises Comfy Level faster. Time and weather gate whether a Pokémon turns up at a habitat at all — though light overrides the clock: a night Pokémon spawns at any hour if its habitat sits somewhere dark such as a cave or underground, and a day Pokémon spawns at night if its habitat is ringed with light.

Give or place anything matching these and both friendship and Comfy Level rise much faster — a matching item lays down with a bigger sparkle. For a Pokémon with the Trade specialty, matching items are also worth 50% more on the scale.

1 Lots of water

30+ items

Resort hammockTable settingPaper Party cupsSoda floatShaved iceModern sinkToiletSinkBathtime setCleaning suppliesShowerBathtubBouncy blue bathtubHumidifierFunky diffuserWater basinCanoeInflatable boatBeach parasolHorsea fountainFire hydrantSprinklerMystic WaterWater pillar quarterHoppip water bottleJuice trioTeaware setBottled shipGyarados fountainBubble machine

2 Ocean vibes

35+ items

Resort stoolResort chairResort sofaResort bedDeck chairBeach chairResort hammockShip's WheelSandboxInflatable boatBeach parasolHorsea fountainFishing rodHarbor streetlightShell lampResort lightMarine chestMarine closetMarine tableOrnate standMarine chairOrnate chairMarine sofaMarine dresserBottled shipDecorative Dive BallDecorative Lure BallWindup InkaySand toysPrimarina statuePearl streetlightSand bedSwim ringBig swim ringBeach volleyball set

3 Nice breezes

9+ items

FanAir conditionerPinwheelsTidal BellModel space shuttleCeiling fanWeather vaneLarge ventilation fanChimecho wind chime

4 Cleanliness

14+ items

Waterproof seatLarge mirrorModern sinkWashing machineToiletSinkTowel rackBathtime setCleaning suppliesShowerBathtubBouncy blue bathtubWater basinCooler

5 Slender objects

49+ items

Vine ropeTwinePaper Party cupsSmall vaseTall potted plantFlat-leaf plantTwisted potted plantFancy penShowerDecorative plant shelfVine wall decorationSlender candleWooden birdhouseFishing rodIron pipesMushroom streetlightTown streetlightHarbor streetlightChic streetlightDouble streetlightDesk lightLuxury lampFluorescent lightBerry hanging lampDestiny KnotWing Fossil (right wing)Wing Fossil (left wing)Wing fossil (body)Wing Fossil (tail)Headbutt Fossil (body)Headbutt Fossil (tail)Shield Fossil (body)Shield Fossil (tail)Despot Fossil (body)Despot Fossil (legs)Despot Fossil (tail)Tundra Fossil (head)Tundra Fossil (body)Tundra Fossil (tail)WireMetal chainRopeBroken streetlightInflatable SudowoodoTelescopeChimecho wind chimeDangling streetlightPearl streetlightLampion

Flavour: spicy

9 foods

Fresh carrotCrouton saladElectrifying soupHealthy soupCarrot breadBread bowlChili sauceExplosive hamburger steakRed-hot smoothie

Two caveats. The game lists these five in a fixed order, but no source says the first counts for more than the fifth — the numbers are the in-game order, not a strength ranking. And the item lists are incomplete: Serebii marks them as still being filled in, so each count is a floor, not a total.