Damp Under Bathtub and Cracks in Grout

[jmw]

I recently took the side off of my bath.

Underneath the bath there are (quite obvious) signs of damp. A small area of the wall seems to have disintegrated because of this.
https://drive.google.com/file/d/0B6k_InU8-ToxLVNHT2RNVWtqdzQ/view?usp=sharing
https://drive.google.com/file/d/0B6k_InU8-ToxQTBJdldJdlBSQTQ/view?usp=sharing
https://drive.google.com/file/d/0B6k_InU8-ToxdG9oWUt2dVFSXzQ/view?usp=sharing


I cannot see evidence that the pipes are leaking. The sealant also seems to be intact. However, the grouting in the tiles above the bath on this same wall has cracks. I assume this is the point of ingress for water.
https://drive.google.com/file/d/0B6k_InU8-ToxZzYwN093U281QUk/view?usp=sharing


To say I'm new to DIY/home maintenance is more than an understatement, so I don't know where to start with tackling. Any advice is greatly appreciated.

[jenniferslauth]

Check the ceramic tile walls surrounding your tub or shower. This tile needs periodic maintenance; cracks can develop in the grout between the tiles, allowing moisture to seep through. To stop the leak and prevent further damage to the underlying plaster or drywall, you'll need to seal all the places where water can penetrate.