How to stop water seeping underneath gap between bath and floor?

Seal around the bath and the floor

You can fill the gap with Sanitary silicone

seal the gap with a pvc trim and seal with silicone

By glueing in place to stop future movement and the seal with a sanitary bathroom sealant.

change the connection

You need a grout and after that silicone to fix it.

There is normally a bath panel on the side of the bath if there is a gap underneath it then you could silicone it but with a 1.2 cm gap you could fit a pvc trim along the bottom of the bath and silicone around it like a skirting board of some sort going hard down to the tiled floor.

There are bath beadings for that hight that goes around the bath, and to be fitted with water proof sealant, which gives a better life time span.

Hi where is the water coming from?

You can use a waterproof sealant or caulk to fill the gap between the bottom of the bath and the tiled floor. Here are the steps you can follow:

Clean the gap thoroughly to remove any dirt, debris, or old sealant using a scraper and a cleaning solution.
Measure the length and width of the gap to determine how much sealant you will need.
Cut the tip of the sealant tube at a 45-degree angle to fit the gap and load it into a caulking gun.
Squeeze the trigger of the caulking gun and apply a continuous bead of sealant along the gap between the bottom of the bath and the tiled floor.
Use a caulk smoothing tool or your finger to smooth the sealant bead and remove any excess.
Let the sealant dry completely according to the manufacturer's instructions before using the bath.
It's important to choose a waterproof sealant that is specifically designed for use in bathrooms and can withstand exposure to water and humidity."

It can be easily fixed with the help of sealants for plastic surfaces like silicon to avoid seeping underneath.

The gap shouldn’t be that big, but I’ve seen people dealing with this problem by installing a plastic beading across and the put silicone over the joints to make it waterproof.

To prevent any water leaks from baths'sinks'toilets or shower trays it has to be silicone and sealed to prevent any leaks making sure all gaps have been sealed correctly.

There is normally a bath panel on the side of the bath if there is a gap underneath it then you could silicone it but with a 1.2 cm gap you could fit a pvc trim along the bottom of the bath and silicone around it like a skirting board of some sort going hard down to the tiled floor.