I could submerge you could submerge she could submerge we could submerge you could submerge they could submerge
V-ing form
I could be submerging you could be submerging she could be submerging we could be submerging you could be submerging they could be submerging
Perfect
I could have submerged you could have submerged she 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 she 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 she 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 she 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 she 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 she 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 she submerge? could we submerge? could you submerge? could they submerge?
V-ing form
could I be submerging? could you be submerging? could she be submerging? could we be submerging? could you be submerging? could they be submerging?
Perfect
could I have submerged? could you have submerged? could she 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 she 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 she 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 she 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 she 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 she have been submerging? couldn't we have been submerging? couldn't you have been submerging? couldn't they have been submerging?