I've even heard some Adventist ministers state that hell is simply "the grave." I can't agree with that, because if that were true, then everyone would go to hell, regardless of their faith.
Keep in mind that this is one of the areas where the KJV does a poor job of translating. All but one of the OT references to "Hell" in the KJV are actually to "Sheol" which indeed does refer to the grave. The Septuagint translated the Hebrew Sheol to Hades (which is Greek mythology is merely the abode of the dead and not the abode of the wicked dead) and the term is also used for 10 of the 22 NT references to "Hell". (The NIV translates the OT Sheol to "realm of the dead" or other similar phrases, while leaving NT uses of Hades as Hades.)
Then there is Ge Hinom (in Greek Gehenna) which is used one time in the OT and and 11 in the NT. That refers to the garbage dump of Jerusalem where the garbage was burned up and is translated as Hell, the place where the wicked shall be destroyed in both body and soul, in its NT appearances by both the KJV and NIV. (The OT reference is treated as a literal reference to the garbage dump.)
Last but not least there is one use of Tartarus in 2 Peter 2:4 which both the KJV and NIV translate as Hell. In Greek mythology, it was a portion of Hades where the wicked were punished. In 2 Peter (as well as the non-canonical 1 Enoch) Tartarus is given as a place where fallen angels were bound.
So it's not the case that the Bible is literally saying everyone goes to Hell, but rather that a poor choice of how to translate Sheol in the Hebrew Testament makes it seem like that is the case in the KJV.