AttackInk Spurt
Flip a coin. If heads, whenever the Defending Pokémon tries to attack, your opponent flips a coin. If tails, that attack does nothing. (This effect lasts until the Defending Pokémon evolves or is Benched.)

Horsea is Pokédex #116, generation 1 (Kanto). Misty's Horsea is a Basic Water Pokémon with 50 HP. The card lists level 16. The card lists Seadra, Seadra (#117) under evolves to.
Misty's Horsea sits at 87/132 in Gym Challenge, position 87 of 132. Before it is 86 Lt. Surge's Voltorb, and after it is 88 Misty's Magikarp. The set belongs to the Gym series. It was released on 16 October 2000. The printed size is 132, and the checklist is the same length. The listed rarity is Common.
The attack Ink Spurt lists 20 damage. The cost is Water, Water. Flip a coin. If heads, whenever the Defending Pokémon tries to attack, your opponent flips a coin. If tails, that attack does nothing. (This effect lasts until the Defending Pokémon evolves or is Benched.) Weakness is Lightning ×2.
Horsea (#116) has 27 other cards in the catalog. Those other cards are in 22 sets. The other printings with a release date run from 1999 to 2024. The earliest other card is Horsea 49/62 in Fossil (1999). That card is named Horsea, while this one is Misty's Horsea. That card lists 40 HP, and this one lists 50 HP. Both list the rarity Common. Mitsuhiro Arita illustrated that card, and Ken Sugimori illustrated this one. 18 other cards of Horsea list a different HP.
The illustrator line reads Ken Sugimori. I count 1,112 other cards in the catalog with that illustrator.
Gym Challenge set binder is where a full Gym Challenge set goes. This card fills one slot there. A generation binder holds one card of each species. Horsea can fill a slot in Generation 1 binder (Kanto). Themed lists that include this exact card are Trainer's Pokémon, Kanto Gym Leaders and their Pokémon, and Misty and her Pokémon. I still need this card.
Flip a coin. If heads, whenever the Defending Pokémon tries to attack, your opponent flips a coin. If tails, that attack does nothing. (This effect lasts until the Defending Pokémon evolves or is Benched.)
Gym Challenge, in the Gym series. It was released on 16 October 2000. The printed size is 132.
87/132. It is entry 87 of 132 in this checklist.
Ken Sugimori. The catalog lists 1,112 other cards with that illustrator.
Common.
Horsea #116, generation 1 (Kanto).
Ink Spurt (20).