Can't help with anything on Walsh. Here's info on three other Black Confederate Seamen :

At the Battle Of Sayler's Creek, 4/6/1865, A unit known as "Tucker's Naval Brigade", was attached to Confederate Divisions of Custis Lee and Joseph Kershaw. These two divisions made up nearly one fourth of the retreating Confederate army. At Sayler’s Creek they were cut off by Sheridan’s Cavalry and elements of the Union II and VI Corps of the Army of the Potomac.

Tucker's command was the only unit that didn't break after the first Union charge. Numbering 300-400 men, surrounded by six Union Divisions, Tucker refused to surrender, and ordered a counterattack against the 37th Mass, and 2nd Rhode Island (commanded by Elisha Hunt Rhodes). Withdrawing to a wooded area, these Confederate Seamen repulsed multiple Federal attacks. Tucker’s Brigade was resilient and did so much damage that the Federal generals estimated the "Naval Brigade” to number some 2,000 men. Tucker was ultimately talked into surrendering toward the end of the day.

Among their number were at least three "Free Men Of Color": Charles Cleaper, who first had served with "Simon's Company (Etiwan Rangers)- part of the 1st Regiment S.C. Mounted Militia, James Hicks, and Joe Johnson. They were among the 25 that escaped and later surrendered at Appomattox. It appears that Johnson first enlisted in the 2nd Virginia Cavalry, 4/20/1862. He was wounded at Aldie, 6/17/1863. Had a horse killed at Raccoon Ford, Virginia, 10/11/1863, paid $650.00 for the horse. Transferred to the Navy, 4/2/1864.