The way we build our decks is a compromise of the cards we have available and how good a deck would be irrespective of 'meta' (i.e. built to be as consistent as possible while able to cope with varying strategies). Thus, while some decks are inherently better than others, they're all fairly competitive with each other which I think makes it more fun since anyone can pick up a deck and play.
About the Deck
Around a decade ago my good friend Andrew piloted a Mono Nature Beast Folk rush deck and when he attended a large tournament, people started calling him 'Beast Folk Mafia'. He was a prolific player during the early days but we soon found the deck couldn't contend with Control. To remedy this, we added cards to strengthen the late-game and Water to add draw make it more sustainable (because if you want to make a deck better you throw in water). This resulted in an extremely fun, fluid and balanced deck - a worthy successor to Andrew's nostalgic relic.
2 Craze Valkyrie, the Drastic
3 Magris, Vizier of Magnetism
3 Holy Awe
3 Kolon, the Oracle
3 Aqua Hulcus
4 Brain Serum
2 Thrash Crawler
3 Aqua Surfer
2 Fighter Dual Fang
3 Bronze-Arm Tribe
3 Quixotic Hero, Swine Snout
4 Natural Snare
3 Mana Nexus
3 Skysword, the Savage Vizier
2 Sanfist, the Savage Vizier
Total: 45 - 20 of which are Shield Trigger!
Barkwhip, the Smasher is a very strong addition as it is a more cost efficient pseudo-Speed Attacker. You may also be evolve it onto Quixotic on turn 3 which means your opponent basically has no answer to it until turn 5 unless you break into a shield trigger.
Tajimal, Vizier of Aqua is another strong card that'd fit well in the deck and improves your match-up against Control. It can also evolve into Craze Valkyrie. I would also throw in another copy of Sanfist if I could but don't have extras.
Flood Valve could replace Thrash Crawler if you want to shift from a balanced approach to a more aggressive one. It is more mana-efficient too and easier to obtain. For a more balanced approach you could consider Sarius to up the blocker count and add as fodder for Craze Valkyrie but I prefer this version.
Energy Stream over Brain Serum could also be an obvious change.
Crystal Lancer and the Merfolk engine were considered but were ultimately scrapped due to inconsistency.