Target 1 face-up monster your opponent controls; change it to face-down Defense Position. Once per Chain, when a Trap Card is activated while this card is in your Graveyard: Special Summon this card as a Normal Monster (Aqua-Type/WATER/Level 2/ATK 1200/DEF 0). (This card is NOT treated as a Trap Card.) If Summoned this way, this card is unaffected by monster effects, also banish it when it leaves the field.
Changes 1 face-up monster your opponent controls to face-down.
You can Special Summon this card as Normal Monster when a Trap card is activated (by you or your opponent). Gains immunity towards monster effects.
This card is not treated as a Trap card, therefore spell/trap removal effects does not work on this card.
If this card leaves the Field after it was Special Summoned, banish this monster.
Have weak ATK and DEF.
When you flip this Trap card after it was Set, it is still considered Trap Card, and it will only set a face-up monster your opponent controls, face-down. After that resolves, this card will be sent to the Graveyard.
After it was sent to the Graveyard, you can therefore activate its effect by chaining to another Trap card’s activation. Monsters set to face-down by this card effect, can be flipped face up again.
This card also acts as an easy tribute for Citadel Whale.
In the first place it's indeed just a Floodgate, but you have the option to special summon it from the GY in a chain with another trap card which gives you a free monster that you can use for a tribute summon.
So it's Floodgate + Free Tribute fodder.
a 2 for 1 card.