Overview on when each deck started to flood during the sinking of the Titanic.
Tank Top[]
The Tank Top level was the first to start flooding, as soon as the collision with the iceberg happened at 11:40 PM. The very first areas to flood were the Forepeak Tank, Cargo Holds 1, 2 and 3, Boiler Room 6 and Boiler Room 5 (The Starboard Coal Bunker in its Forward section). The uneven flooding of Cargo Holds 2 and 3 due to the Pipe tunnel separating them into the Starboard and Port sections, and the flooding of the coal bunker in Boiler Room 5 caused a 5 degree list some minutes after the collision. The Pipe firemen's tunnel most likely started to flood at about 11:55 PM; the water was coming down along the spiral stairs from the G deck level of the Hold 1. Some believe that the starboard wall between the cargo hold and the fireman's passage broke at 11:49, killing Carpenter Hutchinson during his inspection and blasting through the port wall, flooding the firemen's tunnel. It's theorized that Boiler Room 6 filled at 12:30, and that Boiler Room 5 flooded at 1:05 A.M., when water was reaching D-Deck, Boiler Room 4 flooded at 1:50 A.M., BR3 at 2:16 A.M. BR2 at 2:17, BR1 at 2:19, RER at 2:19, and the Turbine and Electric Engines and the Propeller shaft didn't flood until the air pockets imploded sometime after the ship went down.
Orlop Deck[]
The Orlop Deck was the next deck up, above the Tank Top, located only in the bow and stern sections of the ship; the boiler rooms and reciprocating engines took up the space amidships where the Orlop deck would be. This deck started to flood at around 11:45 PM - 11:50 PM, as soon as the forward three cargo holds were flooded. The Mail Room was located in the forward Orlop Deck and started to flood around this time. By 11:52 PM there were just 2 feet left until the room was fully flooded, according to the Fourth Officer Joseph Boxhall.
G Deck[]
G Deck had the lowest passenger spaces on the entire ship, which were split into the bow and stern sections. While the third class cabins were in both forward and aft, the second class occupied only the aft section of the ship. The water reached G Deck at about 11:55 PM, entering the Post Office and Baggage Room and the Squash Court through the vents at the floor level. The Mail Clerks were trying their best to save as much mail as they could starting with the moment when the water entered the Mail Room one deck below. Now, they were trying to haul the bags of mail up to the next deck. The Third Class passengers were the first passengers on board the ship to witness the incoming water, just as soon as their cabins in the forward section on the deck started to submerge at about 12:05 A.M.
F Deck[]
Water entered F-Deck at about 12:15 A.M. There were more Third class cabins located on this deck in both the forward and aft sections of the ship. Also this deck had some of the first class facilities. These were the Swimming Pool and Turkish Baths. The Swimming Pool has started to flood most likely as soon as the water started to flood Scotland Road and reached the stairs leading down to the linen rooms on F deck, at around 12:40 AM - 12:55 AM. Meanwhile, the Turkish Bath section of the deck was reported to start flooding via the stairs coming from the Grand Staircase landing located on the deck above by the steward Wheat at the time period of 12:45 AM - 1:15 AM. The further flooding of F Deck has also continued via the staircases coming from Scotland Road on E deck. The Third class Dining Room flooding in the middle of the ship may have added to the breakup at 2:18 A.M. and it started flooding at a time period of 12:50 A.M.
E Deck[]
The E Deck flooding, as seen in the 1997 film
The water had reached E-Deck at about 12:30 A.M. Minutes before that, at about 12:20 AM, stewardess Annie Robinson found the staircase leading to the Post Office and squash court flooded, having only 6 steps being dry just at the top. Seaman Poingdestre while returning to the seamen quarters located on this deck at the front section testified that the wooden bulkhead separating the quarters from the Third Class area had collapsed and flooded the area in which he was located up to his waist or so. It happened at around 12:20 AM - 12:35 AM. At around 1:00 A.M. water reached Scotland Road. The flooding of this very long hallway, which was 9 feet wide, changed the starboard list into a port list which increased during the later stages of the flooding. E deck was the lowest deck with First Class cabins on the ship. Water reached the Grand Staircase Landing at 12:35 A.M. and reached the Third Class Dining Room by 12:50 A.M. , the E-Deck Grand Staircase submerged at 1:20 - 1:45 A.M. and submerged the Third Class Dining Area by 12:40 A.M. and didn't reach the aft areas until after 2:00 A.M.
D Deck[]
The First Class Reception flooding, as seen in the 1997 film
D deck started to flood at around 12:45 A.M, starting with the front section where the crew quarters and the third class open space were located. The top of the spiral stairs for the firemen was also located in this area. There were more of the first class cabins on this deck together with the First Class Reception Room and the First Class Dining Saloon. The First Class cabins on this deck started to flood at around 1:10 A.M, while the Reception Room started to flood at about 1:20 AM - as soon as the water progressed forward. The whole Dining Saloon disappearead around 1:35 A.M. and reached the Pantry.
C Deck[]
C deck was the most lower deck with the open outdoor spaces, having the Aft Well Deck and the Forward Well Deck. The Forward Well Deck started to submerge at about 1:15 A.M., as soon as the port list increased, thus letting the water start to come into the deck from the left side. The entire middle section of the ship was given to the first class cabins and suites. First Class Passenger Emily Ryerson, while being in lifeboat 4 which was just lowered by the time around 1:50 AM noticed that the water was entering one of the First Class cabins through the portholes. The cabin was most likely located on C Deck. By 2:00 A.M or so the water had reached the Grand Staircase onto B-Deck. By 2:08 water would be pouring into the cabins on C-Deck and submerging the Grand Staircase. By 2:14 those cabins would be submerged but the midship and aft ones would be dry. By 2:16 A.M. the midships cabins would submerge---then at 2:18 the rest of them sank, and areas from the Postal Saloon - Second Class/First.
The Well Deck flooding, as seen in Titanic: Honor and Glory.
B Deck[]
B deck was split into three sections. The forward part was the Forecastle deck, the middle had the largest first class cabins and suites, the a la Carte restaurant and the Café Parisien. The Second class Smoking room was also found on this deck, along with private promenades for each of the classes. The aft section was the Poop Deck. The Forecastle deck started to submerge at around 1:15 A.M, while the First Class areas located on these deck, especially the First Class forward Promenade started to flood at around 1:30 A.M.. The Poop deck was the last area of the ship to go underwater, and was flooded at 2:20 AM.
A Deck[]
The forward promenade deck flooding, as seen in the 1997 film
A-Deck was one of the last decks to flood and was entirely suited to First Class, located in the middle section of the ship. There was the first class promenade, some of the first class cabins, the reading and writing Room, the Lounge, The Smoking Room, the Palm Court and the Verandah. Water reached this deck at about 1:50 - 1:55 A.M., as described by the passengers Woolner and Steffanson while they jumped into the already lowered Collapsible D from the port side.
Grand Staircase[]
The Base of the Grand Staircase (E Deck) started to flood at around 12:45 AM - 1:15 AM, while the top of the Grand Staircase didn't flood until the very end, 2:12 A.M. Steward Wheat testified that the Turkish Bath section of F deck started to flood just as soon as the water reached the base of the Grand Staircase by coming from the starboard hallway, at around 12:45 AM - 1:10 AM. Just some time after him, another steward Frederick Ray reached the Grand Staircase on this Deck and found it starting to flood already by coming from both Scotland Road and the starboard hallway, meaning that the starboard list was already eliminated by this time. At 2:12 A.M, the Grand Staircase dome imploded because of the water pressure. While James Cameron was filming the flooding scene of the Grand staircase, the staircase broke and lifted off its foundations due to the water. It is theorized that this could have happened in real life too.
Boat Deck[]
The Boat Deck flooding, as seen in the 1997 film, but at too low an angle
The Boat Deck didn't flood until around 2:05 A.M. just 15 minutes before Titanic's final moments. Her head trim was now 9-11 degrees and her port list decreased to almost zero. At this point, most people were running for the Poop Deck, as that was the final place to flood. The Boat Deck was where all of the 20 lifeboats were stored, and this is where the main evacuation efforts took place. At 2:07 A.M., Titanic took a dive forward, and once the Bridge was flooded and the forward section of the Boat Deck was going underwater, the Titanic's final plunge began. The first funnel was reached around 2:10 A.M. and she fell forwards. The sea was around the base of the second funnel at 2:15 A.M. Just then, the ship's stern started to rise from the water, and at 2:18 A.M. the angle of the stern reached 45-70 degrees, only two funnels were clear from water and then her lights went out and the ship split in two, just in front of the third funnel. The Boat Deck sank completely at 2:20 A.M. when Titanic went down vertically.