We were just singing this one late last night at a family gathering, which is very similar to the first version posted but has some nice verse variations. It used to be a favorite of my uncle who only would sing it when he thought us young ones were safely asleep:

OLD SHE-CRAB-II
(Ipcar Family Version)

Well the old she-crab was a-sittin' on a post,
Shallow-who, shallow-who,
Well the old she-crab was a-sittin' on a post,
When 'long come a fisherman,
Took her home to roast,
Sing ring-a-long, ring-a-long, roo.

When he got home his old woman was asleep,
Shallow-who, shallow-who,
When he got home his old woman was asleep,
So he put it in the chamber pot
The better for to keep…

The old woman got up for to do her due,
Shallow-who, shallow-wh,
The old woman got up for to do her due,
That crab reached up,
Grabbed her by the flue…

The old woman hollared as she lept in the air,
Shallow-who, shallow-who,
The old woman hollared as she lept in the air,
There's a devil in the pisspot
That's grabbed me by the hair…

The old man knocked the crab off with the handle of a broom,
Shallow-who, shallow-who,
The old man knocked the crab off with the handle of a broom,
And he and the wife chased the crab around the room…

The old she-crab scuttled out the door,
Shallow-who, shallow-who,
The old she-crab scuttled out the door,
Dropped off the dock and swum from the shore…

The old she-crab's at the bottom of the sea,
Shallow-who, shallow-who,
The old she-crab's at the bottom of the sea,
Sayin' I might get caught
But they'll never eat me…

Cheerily,
Charley Noble