Is accordingly entering container a watertight container (7)

I haven't cracked this one yet — but the brilliant team at Fifteensquared have:

IS + SO (accordingly), entering CAN (container). A watertight structure, typically used in engineering projects such as building bridge foundations within a body of water: it allows water to be pumped out, creating a dry area to work in. “Container” doesn’t seem quite right because the water is on the outside . . .