| Dredge |
| Enhance |
| Compound |
| Excavate |
| Intensify |
| Complicate |
| Make darker |
| Dig further |
| Dredge, say |
| Make stronger |
| Drill further |
| Keep dredging |
| Become darker |
| Gain intensity |
| Dredge, perhaps |
| Get complicated |
| Get less shallow |
| Excavate further |
| Continue dredging |
| Increase in depth |
| Grow more intense |
| Grow more profound |
| Grow, as sympathies |
| Extend farther down |
| Become more intense |
| Get worse, as losses |
| Get more complicated |
| Become more profound |
| Make more meaningful |
| Become more heartfelt |
| Compound or intensify |
| Thicken, as a mystery |
| Intensify, as feelings |
| Become more complicated |
| Make more navigable, as a channel |
| Become more complicated, as a mystery |