SeaWolf141

Hi all, I was wondering if anyone could offer some advice to help me counter a very eel heavy Idoneth Deepkin list. I am currently playing Stormcast Eternals against an Idoneth player who insist on using all 18 of his eels at once. Currently, I see no way around this aside from using the artefact on characters that forces flying units to re-roll successful hits. Has anyone had any luck countering these eel spam lists?