Is Seasinger legal in Standard, Modern, and Commander?

Seasinger is legal in: Legacy, Vintage, Commander.

What type of card is Seasinger?

Seasinger is a Creature — Merfolk. Its oracle text reads: "When you control no Islands, sacrifice Seasinger.You may choose not to untap Seasinger during your untap step.{T}: Gain control of target creature whose controller controls an Island for as long as you control Seasinger and Seasinger remains tapped."

Seasinger

Creature — Merfolk

When you control no Islands, sacrifice Seasinger.<br>You may choose not to untap Seasinger during your untap step.<br>: Gain control of target creature whose controller controls an Island for as long as you control Seasinger and Seasinger remains tapped.