The level's title is derived from the motto of the U.S. Navy SEALs, "The Only Easy Day Was Yesterday".
In the art book, it is stated that originally there were plans for a campaign level that had the player controlling a U.S. Navy SEAL team.
As a nod to the SOCOM: U.S. Navy SEALs series, one of the TF 141 members that assists in this section has the callsign "Boomer," the same name as a SEAL team member from the series, along with "Jester," another reference as well.
On a normally inaccessible lower level of the rig, inside a room, there is an M14 EBR Scoped along with a pile of claymores, which can be picked up.
The M14 spawns with a random amount of ammo, both in the current clip and in reserve.
The guard by the railing near the beginning has only 1 HP.
Whilst under the oil rig, the player can see many fish swimming past. If they look closely, the fish will actually swim through the pipes as well as occasionally through the player's face as they move towards the platform whilst still under the ice.
Ghost is never underwater on this map and only spawns once the first guard is killed.
When the player has killed the guard, the water level suddenly rises.
The soldier that the player drags underwater and kills always has the same model, while the one opposite him will always be different. Likewise, the soldier having a smoke while leaning over the rails will always be the same.
The two TF 141 members who pull Roach from the water are always the same models.
When starting the level, there will be two randomly generated Task Force 141 soldiers. They will stay at the bottom, but when the player breaches the first room and then goes back down, they will have disappeared.
Before planting C4 charges, the player's default weapons are M4A1 SOPMOD and SCAR-H Silenced Thermal Sight. However, when the C4 charge is planted, these weapons become M4A1 Red Dot Sight w/Grenade Launcher and the SCAR-H Thermal Sight, both without silencers and with full ammo stock.
When the player gets to the room on this level with hostages inside, after putting a breaching charge on the first door and before it is detonated, Soap (who always runs to the same door) will have an ID tag that changes from "Captain MacTavish" to "Zach" for about half a second.
Before breaching the second room, an enemy is directly behind the window facing the stairs that the player can vaguely see through the window.
If the player goes prone when planting the C4 and keeps an eye on one of the hostages, they will not teleport out of the room and detonating the C4 will cause the mission to fail.
Soap starts the mission with an MP5K Silenced with Red Dot Sight, but after going prone on the scaffolding, he switches to an M4A1 Red Dot Sight w/Grenade Launcher.
If the player ignores the enemy helicopter when it attacks, it will try to keep the player within its spotlight and will continue to pursue all the way to the top deck. Evading the light causes the helicopter to stay on the lower decks, searching. It will instantly disappear when the player breaches the final room.
If the player plants a Claymore behind the door after he/she places the C4, the guards will get alarmed before Soap says "Plan B. Do it."; the mission will continue normally.