You can buy waterproof caulking made specially for bathrooms at almost all hardware and home improvement stores.
Agree! Caulk for bathroom. Is waterproof and has mildewcides in it.
The best product is a siliconized latex caulk. It will say "tub and tile" on the package. Usually, I use white since most bathroom fixtures are white. Alex fast dry is one brand.
Check for a low-odor formula, as this time of year, opening up windows is not going to work.
I always use silicone caulk. Three tubes with the trigger will repaire a large bathroom. If a hardware or home improvement store is convenient, either buy one tube at a time or make sure the store will refund for extra supplies. Invest a couple of dollars in a caulk smoother tool to push the caulk into seams and corners. Best wishes! 🤶🏻