Anime Deck based on Mako Tsunami's Duelist Kingdom Deck. Contains all cards that Mako used in the anime in that season.
Duelist Kingdom has different rules than the current ones (those would only take place in Battle City), so duelists are able to summon high level monsters for no tributes. This deck was made for fun and wasn't meant for being competitive (there was, however, an attempt to do it considering their decks and rules of that arc and their universe).
Not much is known about his first deck, but I believe it didn't change much from his Battle City one.
But it is clear that, this early on, "Kairiyu-Shin" (Leviathan) was his ace card.
Mako probably also had Legendary Fisherman and Fortress Whale around this time, they just weren't shown. His Tornado Wall strategy would probably be too much during this era, so let's just give him that in Battle City.
Notice that, some of the monster choices, are there because of Fortress Whale's materials on the games (I went for that approach for Duelist Kingdom Decks). They also heavily implied that he has a Raigeki in the deck, especially in the games (which I also checked and used to build this deck - I'm looking at you Duel Monsters 1).
His tactic against Yugi (on his first duel) was mostly just hiding his monsters underwater for a surprise Sea Stealth Attack (but for a supposed fair duelist, he wasn't doing much differently than Panik, so why wasn't he called out?).
And for those saying that the "Attack the Moon!" was bs in this Duel, you might also try to remember how Yugi's Equip Spell indirectly raised the tides (that was one weird backfire, but alright). Yugi finished the Duel with Curse of Dragon AND Burning Land, which destroys all Field Spell cards - getting rid of Umi, so it wasn't totally out-of-nowhere, right? Well I'd like to believe that but we already know how Duelist Kingdom rules were something else...
I added those 2 newer cards to the Side Deck in nod to his Duel with Yugi. They were made to refference it and I think they're honestly really cool.