Robot Divers • Late April: The Helix Energy Solutions Group is providing an underwater remote-operated vehicle (or ROV) to support its fleet of 40 subs ranging in size from a large box to an SUV. Initial efforts involved ROVs such as Helix's Quest (pictured above) using manipulators to manually close off the blowout preventer that's gushing oil. The ROVs were unable to trigger the valves.

Relief Drilling • May 4: BP put a far-reaching plan into place early: drilling relief wells. This involves drilling into the well system to divert the flow toward other, controlled wellheads, leaving the leaking well dry. To get it done, BP deployed two rigs, known as Development Driller 2 (pictured above) and 3. The problem? The new wells won't be ready until August, leaving them as a last resort.

The Big Dome • May 7: The first use of a containment dome, and the largest deployed at the site. It measures 40 feet high with a base of 24 x 14 feet, and was intended to seal off the leak so that it could then be funneled up to a ship by way of a pipe. Instead, hydrated crystals and water collected inside it, creating a blockage and giving it troublesome buoyancy. It now sits on the sea floor. (NYT)

The Little Dome • May 12: The second containment unit, a cofferdam called the "Top Hat," is only five feet tall with a base four feet in diameter. The plan was to use ROVs to inject the dome with methanol to act as antifreeze, but the "Top Hat" plan was abandoned — apparently in favor of a more immediate solution. However, now it's back in play. (WSJ)

Riser Insertion Tube • May 14: Rather than stop the flow altogether, BP tried some damage control by running a "riser insertion tube" down into the wellhead. With a diameter of four inches, the tube doesn't cover the well's 21-inch-diameter pipe, though some of the oil has been successfully pumped up to Transocean's drillship, Discoverer Enterprise (pictured above).

Top Kill • May 26-28: Containing the leak didn't work, so BP tried clogging it. The plan? Pump a bunch of mud-like, heavy drilling fluid into the well, which is known as a "top kill." Helix spearheaded the effort with Q4000, a mobile offshore unit (pictured above, right), but 30,000 barrels of mud later there was no luck. BP had similar results with a "junk shot," which clogs a pipe with refuse. (CNN)

Cut & Cap • June 1: One of BP's most recent efforts involved a similar approach as the riser tube lowered down by the Discoverer Enterprise. Known as a "cut and cap," an ROV wielding a diamond wire cutter would cleanly trim one of the damaged pipes so that a customized cap could be put over it, and then oil could be pumped up to the Enterprise. The cutter jammed and the plan was scrapped.

Cut & Cap 2 • Now: With the wire cutter out of commission, BP brought in the big guns with an 18-foot-long pair of demolition shears. The cut isn't as precise — which means the cap won't fit as snugly — and the danger here is that the leak could get worse. The cut has since been made and, as of this writing, the "Top Hat" (shown earlier) is being put into place to help stymie the flow of oil.

Fleet Overview: This image, created by BP, shows you the fleet makeup and positioning of the vessels involved in the cleanup, such as the Q4000 and Discoverer Enterprise. (Deepwater Horizon Response)