Notes & Combos
The idea of the deck is basically that Exagard is a WATER attribute Xyz and can provide board value while enabling the shark cards, and because your Materiactor combo makes 2 free level 3s for any Xyz plays after Exagard, you can make Virtue in place of a card like Hieretic Seals or Gossip Shadow because it's something you would want to run for Sharks anyway.
If you want to change this list up its probably better to run Mad Lobster over Dragoons for Roars gy effect, you can also drop the extra Zeptowing because its a little less useful than it is when playing materiactor primite and if you still wanna summon non waters you can drop Abyss Shark and just search Hydrojet early but you lose access to making Exgard off of 1 Big jaws and need a spell card to make Stealth Kraken.
Heres a combo: 1 Primite Roar + 1 Surfacing Big jaws
Step 1: Activate Primite Roar and Special Summon 1 of your normals from your deck.
Step 2: Special Summon Big Jaws and Search Abyss Shark
Step 3: Special Summon Abyss Shark and add Hydrojet
Step 4: Xyz Summon Exagard using your 3 normal and Big Jaws
Step 5: Special Summon jet and mill Revival Splash
Step 6: Use Exagard detaching the normal to get Critical
Step 7: Xyz Summon Stealh Kragen using hydrojet and Abyss
Step 8: Set Critical
End Board: 1 Omni or a Bounce, Quick effect pop with Kragen, and Revival Splash in gy to make Veiss or Abyss Dweller with 1 of your used up negated on your opponents turn. Also if you made this going second you can just pop an opponents monster with Kragen attack with Exagard and Kragen and make Veiss during the battle phase with Revival Splash to clean up the game with its double damage (because of Abyss Shark), double attack, piercing battle damage.
Character limits forced me to put the second combo in the comments, sorry for any grammer mistakes and because no one reads this far some times i use Materiactor Howl to declare little D. because its funny and i need it in the gy.