In order to access Silent Woods from Kwolok's Hollow, you normally need to clean the water but it is actually possible to swim through the dirty water if you have Regenerate and enough energy and health. The amount of health you will need depends on the difficulty you are playing on. This amount can be greatly reduced by having Water Dash or the Resilience shard. You can also use godmode to remove the health and energy requirement entirely.
This is how the scene looks with the debug renderer on.
There is 3 important elements for this trick: the wall you need to break, the tentacle at the center of the screen which will shoot a projectile you will be using to break the wall next to the tentacle and the small part where you can breath before the tentacle.
You first need to swim through the dirty water to reach the surface at the left of the tentacle. If you surface there and hold left, you will be standing on a small ledge, outside of the water. From this point, you can now use Regenerate for the second part of the trick: breaking the wall.
In order to break the wall, you can either stick to it and wait for the tentacle to shoot at you, or bash the tentacle's projectile into the wall, which is the part we'll focus on. The bash is pretty precise: if you hold down while swimming against the floor on the left of the right mouse ability, you'll get stuck in the perfect position for the bash. Then wait for the tentacle to shoot at you and bash the projectile as soon as possible. Finally, aim your bash to be just a bit lower than the tentacle. If it's aimed correctly, it should hit the wall and break it.
After you broke the wall, you want to return to the ledge on the left in order to heal up. You can then swim to the other side of the wall the wall you just broke and reach Silent Woods. This part requires a lot of health, you want to time when you release your bash so the tick of water damage ends up on the invulnerability frames bash gives you.