As the early midgame WRE, how do I catch a navy horde that keeps running away?

So I finally returned to Attila which many here mention as so good in so many aspects, despite having some almost gamebreaking ones like the worst missile troops behaviour of any TW. I'm surely liking it, this WRE really is a different beast, but the cracks in game design are beginning to show.

I'm doing fairly well and have kept most of my territory in turn 60 (only Hard mode mind you), but this last remnant of Jutes in the western Mediterranean, a pure navy, is being a major annoyance. It has 50% extra movement itself and keeps avoiding the navy I sent to catch them with that extra 25% from forced march. Agents don't work in the sea so there's no way to hinder them.

My navy, maxed regarding anything movement related, has +65% movement range, which is not enough. All my sea battles until now have been a shitshow of casualties, so I'm not confident in sending a smaller navy to bait them, as I do with land hordes.

The bastards keep growing by hiring mercenary ships, forget raiding, they'll be a major menace to my land armies if I get them into the area where they are. Is waiting for them to clash their future stack of tiny sea mercenary units with my level 2 garrisons the only outcome in sight? With only one horse unit per settlement, this could take dozens of turns.

Any assistance with guiding those barbarians to their beloved Valhala would be much appreciated.

\[Btw, meanwhile an ally of mine has been running after another cowardly Frank horde stack around half of Gallia and Iberia, after I got tired of it. Even with spies hindering their advance they just run again... I'd much rather prefer a half suicidal campaign AI than this annoying mess.\]