I must water-ski you must water-ski he must water-ski we must water-ski you must water-ski they must water-ski
V-ing form
I must be water-skiing you must be water-skiing he must be water-skiing we must be water-skiing you must be water-skiing they must be water-skiing
Perfect
I must have water-skied you must have water-skied he must have water-skied we must have water-skied you must have water-skied they must have water-skied
V-ing perfect
I must have been water-skiing you must have been water-skiing he must have been water-skiing we must have been water-skiing you must have been water-skiing they must have been water-skiing
Negation
Simple form
I must not water-ski you must not water-ski he must not water-ski we must not water-ski you must not water-ski they must not water-ski
V-ing form
I must not be water-skiing you must not be water-skiing he must not be water-skiing we must not be water-skiing you must not be water-skiing they must not be water-skiing
Perfect
I must not have water-skied you must not have water-skied he must not have water-skied we must not have water-skied you must not have water-skied they must not have water-skied
V-ing perfect
I must not have been water-skiing you must not have been water-skiing he must not have been water-skiing we must not have been water-skiing you must not have been water-skiing they must not have been water-skiing
Interrogative form
Simple form
must I water-ski? must you water-ski? must he water-ski? must we water-ski? must you water-ski? must they water-ski?
V-ing form
must I be water-skiing? must you be water-skiing? must he be water-skiing? must we be water-skiing? must you be water-skiing? must they be water-skiing?
Perfect
must I have water-skied? must you have water-skied? must he have water-skied? must we have water-skied? must you have water-skied? must they have water-skied?
V-ing perfect
must I have been water-skiing? must you have been water-skiing? must he have been water-skiing? must we have been water-skiing? must you have been water-skiing? must they have been water-skiing?
Interro-negative form
Simple form
must I not water-ski? must you not water-ski? must he not water-ski? must we not water-ski? must you not water-ski? must they not water-ski?
V-ing form
must I not be water-skiing? must you not be water-skiing? must he not be water-skiing? must we not be water-skiing? must you not be water-skiing? must they not be water-skiing?
Perfect
must I not have water-skied? must you not have water-skied? must he not have water-skied? must we not have water-skied? must you not have water-skied? must they not have water-skied?
V-ing perfect
must I not have been water-skiing? must you not have been water-skiing? must he not have been water-skiing? must we not have been water-skiing? must you not have been water-skiing? must they not have been water-skiing?