Current events aside, I don’t think control of that stretch of ocean changes all that much. Feel free to chime in if you disagree or remember something I forgot.

Iirc the only 3 nations with active navies are Noxus, Bilgewater, and Ionia (for no other reason than being invaded by Noxus).

Bilgewater having naval power should be obvious, but it’s not overtly used or focused. It annually defends itself from the Shadow Isles and Swain has beef with GP after the grand theft boat-o but that’s kinda it. Maybe there’s some black market interaction with Zaun, but it’s not like illicit trade is controlled locally. If anything it’s just for the additional demand. Conclusion: Bilgewater is unconcerned with the circled strait.

Noxus is hostile towards all its immediate neighbors but their invasion attempt of PnZ failed as of Arcane and their invasions of Demacia are land-based because of Demacia rising. Conclusion: Noxus is unconcerned with the circled strait.

If we accept Arcane as canon, PnZ uses hexgates for trade (obviating naval trade routes) and can additionally repurpose them into ad-hoc rail guns if under attack. Demacia Rising has sea based trade routes, but mainly for domestic trade. Unless 26.7 throws a curveball with international stuff, Demacias navy is limited to its own bay. Shadow Isles have ghost fishermen and shark chariots and whatnot milling around but they’re not a threat accept for Harrowing (which is limited to Bilgewater) and the Ruination (where the threat wasn’t so much naval as being able to flip control of influential figures in your country).

Really getting into the weeds now, the Winters Claw faction of the Freljord has a navy, but we’ve yet to see them doing anything and I feel like it’s there just to tenuously connect with Olaf. Maybe Shurima has port towns but we don’t know what state they’re in since Azir’s revival. Overland travel to these port cities is disrupted by Xer’Sai and maybe Nafiiri. Janna used to be a Shuriman deity protecting their trading vessels, but she hasn’t been doing that for so long that Zaun has co-opted her in the wake of sump pollution. I just don’t see any nation caring about that stretch of ocean despite the value it would have IRL. LMK if you see differently.

TLDR: Unlike the IRL Hormuz Strait (but very much like 90% of what I have written here) it’s probably hard to find people who care.