One of the few splinters that have been OP even as a begginer is the water splinter. With so many magic monsters that are low mana and a small buff from Albric Stormbringer, I think many of the newer players can agree it's one of the tougher splinters to go up against.
Recently, with the new reward cards that's all changed. With this deck, you increase your odds of beating the water splinter substantially.
Owster Rotwell is a relatively cheap card for new players to gain a huge advantage. The magic reflect buff this summoner gives plays a huge roll when going up against the water splinter given that it has so many low mana magic cards. Fortunately, those cards are typically lower health so the magic reflect will take them out no problem.
Next up on the list is the Venari Bonesmith. This card in my opinion is undervalued and I am personally working on leveling it up. The card has a relatively low mana cost and the Life Leech ability makes it worth every penny. With this summoner and monster, you become a formidable opponent and increase your chances against the water splinter substantially.
I've linked two battles below that show what I'm talking about.
https://splinterlands.com?p=battle&id=sl_fbbeba66124ad2c6db258b8b222017a0&ref=tscott
https://splinterlands.com?p=battle&id=sl_300f47d20b9f4790ee8605cdb6ef49be&ref=tscott