Okay, okay, I know. I know monocolor fish > U/W fish, and that trying to be cute in Modern gets you killed. At some point, I'll probably revert this all back to mono blue. But, in the meantime...

Creatures (28)

4x Cursecatcher

2x Harbinger of the Tides

4x Lord of Atlantis

4x Master of the Pearl Trident

4x Master of Waves

4x Merrow Reejerey

4x Silvergill Adept

2x Sygg, River Guide

Spells (13)

4x AEther Vial

2x Dismember

4x Spreading Seas

3x Vapor Snag

Lands (19)

2x Cavern of Souls

2x Hallowed Fountain

2x Island

4x Mutavault

1x Oboro, Palace in the Clouds

4x Seachrome Coast

4x Wanderwine Hub

Maindeck, this is essentially running a marginally weaker manabase in order to play Sygg, River Guide in the traditional Kira, Great Glass-Spinner flex slot. Sygg has the advantage of being a two drop over a three drop, and having particular synergy with AEther Vial plays. With two mana open, and a vial on 2, Sygg plays for Fish like Rattlechains does for Spirits. And he's printed islandwalk, so he can sometimes sneak in some damage in suboptimal board states. But the point of going /W is for the board options here. Currently:

Sideboard (15)

2x Chalice of the Void

2x Kira, Great Glass-Spinner

3x Rest in Peace

3x Stony Silence

3x Swan Song

2x Tidebinder Mage

I'm not strictly satisfied with this arrangement, however. RIP is obviously a big draw for /W, wrecking a whole bunch of archetypes in a single play. Against Affinity, I drop Vials for Stony Silence and have something of a game. It's still a disfavored matchup, but Silence punishes them harder than Hurkyl's. Tidebinder obviously locks out Gofys and other miscellaneous creature-based nonsense.

I'm less sold on the remaining 7 slots. Currently, the idea is to bring in Swan Songs against miscellaneous combo engines, in place of some of the removal. Chalice is a versatile answer to a lot of problems. Kira is... probably weak in the board here, except against extremely heavy removal; this slot could arguably be Spellskites, although I regrettably don't have them at the moment. I'm probably dog meat to Infect.

I'm aware that the absence of Path in a /W variant is tantamount to heresy, and I've strongly considered it in the Kira slot in board. It's absolutely not a maindeck card here because of the skornergy with Spreading Seas; I do not want to lock an opponent off his preferred mana base and then hand that mana base right back to him. There are very few creatures in format where I'd prefer that outcome to just Vapor Snag'ing whatever scared me. Or Dismembering it. Or whatever. It'd be nice to Path a reanimated Iona on blue, but marginal situations are marginal.

Am I overlooking strong options here? Leyline of Sanctity for burn/discard? I'm going to walk this into a blind metagame, so I'm trying to be versatile. Alternatively, feel free to talk some sense into me and get me to drop /W, if you'd prefer!