[Bug][Lost Valley] Lara can clip through bottom of river

[dsb-qa]

Steps to Reproduce

1. At the start of the Lost Valley, head towards the river and turn to the left away from the waterfall
2. Once past the stone column, jump into the water and swim towards the bottom

Expected Result
Lara should not clip through the rocks at the bottom of the river and fall over the edge of the waterfall.

Actual Result
1/10 attempts Lara can clip through the bottom of the river and get stuck.

[dsb-qa]

#86 is a similar issue with potentially the same root cause.