Pokémon GO introduced two new weekly events earlier this year: Spotlight Hour, which saw one Pokémon take over the majority of spawns, giving trainers an option hour-long grind session for that week's choice creature, and Mystery Bonus Hour, which featured an in-game reward such as double catch Stardust, double transfer candy, and so on. Niantic has since combined the two days into one event that has taken place on Tuesdays at 6pm local time. This week's mini-event will be Horsea Spotlight Hour with double catch Candy, and the Shiny Horsea will be available.
Horsea Spotlight Hour is set to be one of the most popular iterations of this weekly event so far. This is a popular Water-type Pokémon from Generation One, and has a three-stage evolutionary line of Seadra and Kingdra, the latter of which adds a dual typing of Dragon. Horsea's Shiny form is a deep seafoam green that turns purple when evolved to Seadra and Kingdra. Horsea will be spawning very densely tomorrow, so players may have to choose between one of two goals to optimize the day: Shiny hunting, or exploiting the Candy bonus.
For a greater chance at Shiny Horsea, which has a rate of one in about 450, the Shiny Check method may work best. This method is when trainers click on a spawn, see if it's Shiny, and flee if it's not. This will cut out the catching process, turning an over twenty-second encounter to just a few seconds. Using this method, exploring a location with dense spawns by foot or in a car can lead to hundreds of Horsea encounters within the hour.
As far as the bonus, double catch Candy will be active not only for catching Horsea, but will apply to any catch. Because Horsea will be spawning non-stop, by the end of the hour, even those casually playing will gave enough Candy to evolve up a Kingdra. However, for those who either already have a Shiny Horsea or aren't interested, this would be a great time to do Rayquaza and Gible raids to double Candy for these rarer Pokémon. That is, if you can find a Gible raid.