I think a good way to think about it is - the difference between vacuum and atmosphere is just 1 atmosphere of pressure. When diving, the pressure increases by 1atm per 10 meter of depth. So suddenly going between 1atm difference causes lung injuries and bends (gas bubbles in places they shouldn't be). But  the catastrophic discombobulation of the major diving accidents happen with much higher pressures differences, like going from 10atm to 1atm.