What are the differences from Dead Island to Dead Island Riptide?

Much of Dead Island's game engine appears unchanged in Dead Island Riptide.

What changes have been made to the game in the jump from Dead Island to Dead Island Riptide?

• Medkits and throwables no longer fill inventory slots.
• There are new types of ammo: harpoon, taser/stun gun, nailgun, and launcher.
• The four original characters return + one new character: John Morgan, the hand-to-hand specialist.
• There don't seem to be developer's craft weapons anymore.
• There's an option to import characters, but it doesn't seem to import items. You can't import from OnLive.
• The netcode is bad.
• Desynchs happen often. Seems to occur consistently if not-the-host operates a vehicle. Desynch is when in one person's game, another player character does not move properly. Their body continues to perform some last motion, like running continuously into a wall or idleing. The only known fix is to rejoin. The desynchee will otherwise play normally, not being able to tell that they have desynched until they must enter a red ring where all players must gather, which becomes impossible. Desynch causes one of the players involved in the desynch to have their own set of enemies.
• Bad netcode may cause a throwable to be thrown at one's feet to other players while otherwise acting normally to the thrower.
• Old blueprints reappear. New blueprints appear too. It seems that items that were once exclusive in Dead Island are now part of the vanilla content in DIR.
• The characters' skill trees seem to have changed in terms of their order and additions. Each character seems to get a Charge skill in the Combat tree, a Spring skill in the Survival tree to get up faster, and a group fury skill in the Fury tree which unlocks the ability to optionally activate a team-based fury effect when one furies.
• Multiplayer player icons and health bars are colour-coded, instead of everyone being red.
• Striker fire firearm mods are now called Hooligan.
• Level cap has been raised to 70.
• There's cosmetic DLC.
• New throwable item: flare. Lights up an area.
• New firearm: Bolt-action and semi-automatic sniper rifles. Use rifle ammo. Slow reload. Seem to do extra damage on head-shot.
• New firearm: Nailgun. Recollectable ammo.
• New firearm: Stun gun. Semi-automatic, five shots per reload. Applies a shock effect, tasing enemies, replacing the debilitating capacity of the discontinued plaguebearing military knife.
• There's a Spot in multiplayer option. Aim at something and spot it to highlight it to others, such as a location to move to, a ladder to climb, an NPC to talk to, or an item to grab.
• New vehicle: boat. Has a boat boost option which is a limited, regenerating resource. If zombies latch on, QTEs may have to be performed to defend oneself. The operator's QTE involves the Use key. Sufficient boat-boosting kills climbers.
• Storage is now available early in an NPC named Henry.
• There are now individual weapon proficiency skills to level up which give a unique bonus at each level.
• New types of mods: Area of effect mods.
• Firearms seem to have new bash options which are activated by the same button as Spot. They lunge.
• New types of zombies appear. Each type is outlined as you progress in Dr. Kessler's Casebook in the options menu.
• New special attack: attack from above. From a high enough position against a zombie close enough, a prompt will appear on their head. Perform with the Use button. Your character will lunge at them and strike them with their body. Cancels falling damage, can miss, and sometimes has lots of ending lag.
• New hand-to-hand weapon: claws.
• New mission type: hub defense. Defend a location against hordes of zombies with progress measured by horde strength on your HUD.
• Minigun emplacements have limited ammo. They can be uninstalled and moved, but only to set locations.
• Functional NPCs pace about.
• There's a weather system which alternates between sunny or suddenly raining.
• New throwable item: throwing knives. They cannot be upgraded, they can be picked up instantly, and all of their different types from the lowest level to the highest are for sale from the start.
• Some water is too deep to sprint in. The fastest way to move through this is to side-hop or back-hop through it.

The difference is basically better graphics for a new game. The playing mechanics are the same and the story line is the same. Riptide adds a "fear factor" into the game with it's bonus scary sound effects.