Swap Frog (SOVR-EN034) - Stardust Overdrive Unlimited

You can Special Summon this card (from your hand) by discarding 1 other WATER monster. When this card is Summoned: You can send 1 Level 2 or lower Aqua-Type WATER monster from your Deck or face-up from your field to the Graveyard. Once per turn: You can return 1 monster you control to the hand; you can Normal Summon 1 "Frog" monster during your Main Phase this turn, except "Swap Frog", in addition to your Normal Summon/Set. (You can only gain this effect once per turn.)