I could submerge you could submerge he could submerge we could submerge you could submerge they could submerge
V-ing form
I could be submerging you could be submerging he could be submerging we could be submerging you could be submerging they could be submerging
Perfect
I could have submerged you could have submerged he could have submerged we could have submerged you could have submerged they could have submerged
V-ing perfect
I could have been submerging you could have been submerging he could have been submerging we could have been submerging you could have been submerging they could have been submerging
Negation
Simple form
I couldn't submerge you couldn't submerge he couldn't submerge we couldn't submerge you couldn't submerge they couldn't submerge
V-ing form
I couldn't be submerging you couldn't be submerging he couldn't be submerging we couldn't be submerging you couldn't be submerging they couldn't be submerging
Perfect
I couldn't have submerged you couldn't have submerged he couldn't have submerged we couldn't have submerged you couldn't have submerged they couldn't have submerged
V-ing perfect
I couldn't have been submerging you couldn't have been submerging he couldn't have been submerging we couldn't have been submerging you couldn't have been submerging they couldn't have been submerging
Interrogative form
Simple form
could I submerge? could you submerge? could he submerge? could we submerge? could you submerge? could they submerge?
V-ing form
could I be submerging? could you be submerging? could he be submerging? could we be submerging? could you be submerging? could they be submerging?
Perfect
could I have submerged? could you have submerged? could he have submerged? could we have submerged? could you have submerged? could they have submerged?
V-ing perfect
could I have been submerging? could you have been submerging? could he have been submerging? could we have been submerging? could you have been submerging? could they have been submerging?
Interro-negative form
Simple form
couldn't I submerge? couldn't you submerge? couldn't he submerge? couldn't we submerge? couldn't you submerge? couldn't they submerge?
V-ing form
couldn't I be submerging? couldn't you be submerging? couldn't he be submerging? couldn't we be submerging? couldn't you be submerging? couldn't they be submerging?
Perfect
couldn't I have submerged? couldn't you have submerged? couldn't he have submerged? couldn't we have submerged? couldn't you have submerged? couldn't they have submerged?
V-ing perfect
couldn't I have been submerging? couldn't you have been submerging? couldn't he have been submerging? couldn't we have been submerging? couldn't you have been submerging? couldn't they have been submerging?