The destructive foray of the Confederate ironclad ram CSS Albemarle from the Roanoke River into Albemarle Sound, North Carolina, on 17 April and her reappearance on 5 May—the day Grant's offensives began—increased Union anxiety over the possibility that the Confederate squadron at Richmond might descend the James, wrest control of that vital stream from the Union flotilla, and wreck Butler's transports and supply ships, stranding his troops in hostile territory where they would be at the mercy of Southern soldiers.

To prevent such an eventuality, Welles sent several warships, formerly ordered to the Gulf of Mexico, to Hampton Roads, Virginia, to reinforce the James River Flotilla.

Late in July, the situation in that river seemed stable enough to permit the Union warships borrowed from Farragut to move on to the Gulf of Mexico.

Repaired and prepared for sea by the Norfolk Navy Yard, Althea departed Hampton Roads in company with three other tugs on the 26th and reached Mobile Bay on 5 August, the day of Farragut's great victory there.

On 12 April, the day Mobile finally surrendered, Althea struck a torpedo (naval mine) in the Blakeley River and sank while returning from a run up that stream in which she had dragged primitive sweep gear in an effort to clear the channels of explosive devices.