I've seen it once and I haven't seen an explanation until now. My wife and I were kayaking on a lake in Northern Sweden and far far away we see a boat that is j

I've seen it once and I haven't seen an explanation until now. My wife and I were kayaking on a lake in Northern Sweden and far far away we see a boat that is just moving slowly, lifted up in the air. It was completely calm and we could not hear it (very far away), it was ghostly.