Water in Trunk

The spare tire well in the trunk of my 99 seville keeps filling up with water. Ive replaced the rubber gasket that seals the trunk but it did not solve the problem. I do have a cracked taillight bu cant see how this would cause the problem. Any suggestions???

Welcome to AF, strip everything out of the trunk down to metal, climb in there have some one close the trunk and water test the car, with a flashlite you should be able to see the point/s of entry, std body shop procedure for this problem.