I think what makes 'What Lies Beneath' so suspenseful at the start of the film is the music, if you just listen listen to the sound of the film, you would know something bad is going to happen, it has very eerie and creepy feel to it, the music is quiet and speeds up, it is quite changes the pitch and the tempo in a very 'scary' way, and then just before it stops it has a sort of whispering murmur. It also has the digetic sounds of the water splashing and then the woman being breathless and panting, which gives away it is a thriller.
Another way it creates suspense it thorough the camera work, as to begin with it is like the camera is moving upwards to the bath tub, hence 'What lies beneath' so the audience knows that there is something 'beneath'. Then there is a close up of the woman's face as she lifts her head out of the water, and it also somehow looks as if there is another face above hers for a second. this close up as she quickly lifts her head above the water makes the audience jump a little. When we see the wide shot of her bathroom and her in the bathroom, it is shot from a very low angle, so it is almost like she is being watched, the low angle also emphasises the 'beneath'.
For my Thriller film, I will strongly take into consideration the choice of music, as straight away it can set a film up. And also camera shots and the movement, I think the look of being followed or watched makes for good thriller, and also the perspective shots. As in reference to 'The Shining' the shots at the beginning were from above as if it was a bird. So in many thrillers these shots are carefully chosen.
The trailer for 'What Lies Beneath' :