Precon Upgrade

This is an upgrade of the 2020 Aesi precon deck. I kept in a number of the elements of it - namely keeping a number of (admittedly sub-optimal) sea creatures like Tromokratis.
Otherwise, I put in a lot of good ramp, took out junk and traps, added more lands, and put in a few win conditions (Expropriate, Scute Swarm).

This deck only runs a single tutor, and that's by design. Sometimes, you just have to close out a game so that people can call it quits for a day/ start the next game (Green Sun's Zenith, find Scute Swarm or Avenger of Zendikar). If it wasn't for that reason, I wouldn't run any. As I've learned, having more tutors will increase the reliability of your deck to find the most powerful cards in your deck every time. So then you find the same creatures every time. And your 100 card singleton deck becomes very reliable, and that's to the detriment of my fun with this deck.
As such, this deck relies on pure card draw from Aesi. Is this an innovative Simic landfall deck strategy? No. It doesn't pretend to be. It's a battlecruiser, that casts big things with a high CMC fairly because it has that much mana available to it. By turn 5 or so, I usually have north of 15 lands on the field, and by then the anti land-destruction meta means it's basically unstoppable - unless someone wins before you do. If you're paying 10 or 12 mana for Aesi, it's unpleasant sure, but you can do it.

But what about the card draw?

You don't need it champ. With Aesi out, I frequently nearly deck myself by the end of a game. Ending the game with sub 20 cards in library is scarily common. Fear the mill decks!
Remember, with Aesi, if you tutor for 1 land with a simple Rampant Growth, you're finding 1 card and putting it on the battle field, and then drawing a second card. With Boundless Realms, you might tutor for say 10 land cards (tbh I usually get 6-8 lands from experience, your mileage may vary), then draw 10 cards - that's 20 cards removed from your library.
Biggest pro tip? Aesi is a MAY ability. You don't have to the draw cards - keep that in mind.

Upgrades

Reasonable Upgrades

These are the kinds of upgrades which will up the efficiency of the deck. May or may not result in you losing friends :)

• Take out Command Tower, Memorial to Genius, probably Mosswort Bridge, Woodland Stream, and put in 3 basic lands and a Thespian Stage (to cheese out Marit Lage with Dark Depths) that way you can find more lands with Boundless Realms. Honestly, with 2 colours, colour fixing isn't your problem. It's running out of lands to play, and you can always tutor for basic lands.
• Augmenter Pugilist // Echoing Equation has useful applications. Either it's a cheap trample 8/8, or we can use it when we're copying the Scute Swarm (more niche tbh, but the 8/8 is almost always relevant for a mere 3 mana, but turning a "I have 16 scute swarms on board and can't go lethal on every player right now, but 16 copies of Molimo, Maro-Sorcerer with 14/14 trample is lethal on every opponent" is a one-trick pony that's more of a 'Win-More' than a real win condition).
• Jadzi, Oracle of Arcavios // Journey to the Oracle. We want the Journey to the Oracle, for those times we have too many of our 47 land cards in our hand to play all at once.
• Tatyova, Benthic Druid. It's an additional commander in effect.
• Fun big green creatures. Titanoth Rex and Impervious Greatwurm are good fun fair magic. This is the kind of route to go down if you want to get out of the sea monster tribe shell a bit.
• If you want to get more into the sea monster tribal, remove Molimo, Maro-Sorcerer, Jin-Gitaxias, Core Augur (only here because I had a spare after buying it for a deck that didn't get much out of it), make another cut and add in Spawning Kraken, Serpent of Yawning Depths, and Breaching Leviathan / Koma, Cosmos Serpent/ Inkwell Leviathan.
• Overrun effects, such as Overwhelming Stampede and Pathbreaker Ibex.
• Ominous Seas. As identified, you draw a lot of cards - might as well weaponise it for a mere 2 mana.

Unreasonable Upgrades

If you want to further upgrade this deck, and lean further into the degeneracy of Simic landfall, then here's how to lose your friends :)

• Add in Reshape the Earth, to give redundancy for the Boundless Realms.
• An Eldrazi Titan with the clause "If this (Eldrazi) is put into your graveyard, reveal it and shuffle your graveyard with your library", like Kozilek, Butcher of Truth. The number of times I've nearly died to mill after drawing too many cards is terrifying. Get yourself this failsafe, and don't go against an Ulamog, the Ceaseless Hunger Deck - unless you can tap it down with the otherwise silly Sea Monster tribal like Slinn Voda, the Rising Deep, Elder Deep-Fiend, or bounce it with Scourge of Fleets or Into the Roil.
• Get rid of the silly Sea Monster tribal like Slinn Voda, the Rising Deep, Elder Deep-Fiend, and Scourge of Fleets. Get real monsters like Blightsteel Colossus, Ashaya, Soul of the Wild, Craterhoof Behemoth, Multani, Yavimaya's Avatar, Vorinclex, Sakashima of a Thousand Faces, Hydroid Krasis, Koma, Cosmos Serpent.
• Cyclonic Rift and Fierce Guardianship for removal. Those 2 cards are worth more than the precon twice over last I checked. On a more serious note, Bane of Progress won't hit our board because there's only 1 artifact in the deck (Expedition Map).
• Add in tutors. Tooth and Nail, Worldly Tutor, Finale of Devastation, these will increase the reliability of your deck to find the most powerful cards in your deck every time.
• More extra turn spells. Walk the Aeons, to get sweet easy mode buyback? Temporal Manipulation, Time Warp, Nexus of Fate, Capture of Jingzhou, and of course that spare Timetwister you have lying around (I'm being facetious here).
• Put in the Retreat to Coralhelm combo (Simic Growth Chamber, Sakura-Tribe Scout). With Sakura and Retreat on the board, tap Sakura to play Simic Growth Chamber, have Simic Growth Chamber bounce itself, untap Sakura with retreat. You now have infinite land ETBs for Aesi to draw your entire deck, or for Scute Swarm/ Rampaging Baloths/ Avenger of Zendikar/ Retreat to Kazandu, etc.