I could sink you could sink he could sink we could sink you could sink they could sink
V-ing form
I could be sinking you could be sinking he could be sinking we could be sinking you could be sinking they could be sinking
Perfect
I could have sunk you could have sunk he could have sunk we could have sunk you could have sunk they could have sunk
V-ing perfect
I could have been sinking you could have been sinking he could have been sinking we could have been sinking you could have been sinking they could have been sinking
Negation
Simple form
I could not sink you could not sink he could not sink we could not sink you could not sink they could not sink
V-ing form
I could not be sinking you could not be sinking he could not be sinking we could not be sinking you could not be sinking they could not be sinking
Perfect
I could not have sunk you could not have sunk he could not have sunk we could not have sunk you could not have sunk they could not have sunk
V-ing perfect
I could not have been sinking you could not have been sinking he could not have been sinking we could not have been sinking you could not have been sinking they could not have been sinking
Interrogative form
Simple form
could I sink? could you sink? could he sink? could we sink? could you sink? could they sink?
V-ing form
could I be sinking? could you be sinking? could he be sinking? could we be sinking? could you be sinking? could they be sinking?
Perfect
could I have sunk? could you have sunk? could he have sunk? could we have sunk? could you have sunk? could they have sunk?
V-ing perfect
could I have been sinking? could you have been sinking? could he have been sinking? could we have been sinking? could you have been sinking? could they have been sinking?
Interro-negative form
Simple form
could I not sink? could you not sink? could he not sink? could we not sink? could you not sink? could they not sink?
V-ing form
could I not be sinking? could you not be sinking? could he not be sinking? could we not be sinking? could you not be sinking? could they not be sinking?
Perfect
could I not have sunk? could you not have sunk? could he not have sunk? could we not have sunk? could you not have sunk? could they not have sunk?
V-ing perfect
could I not have been sinking? could you not have been sinking? could he not have been sinking? could we not have been sinking? could you not have been sinking? could they not have been sinking?