Fintan The Seer. The Mystical Irish Tales, #1

Ireland is young, wild, and untouched when Cessair's people arrive, believing they have found a sanctuary from the world's destruction. Fintan, one of her companions, feels a strange unease in the land itself - the rivers pulse too strongly, the sky hangs heavy, and the animals flee inland as if warned by ancient instinct. As Cessair tries to build a new society, Fintan becomes increasingly aware that the land is rejecting them.
When the first tremors shake the earth, he realises the flood is not a myth but a certainty. His fear is not for himself but for the fragile hope Cessair carries. As the waters rise, Fintan makes a desperate choice that will change the course of Irish myth forever.