Caulking for tub and and standing shower

Being water clean up, I would not put my trust in a wet area in it. I would use a good color matching grout caulk or Silicone, BUT only after you remove the old caulk and dry it out completely. The water you say may have infiltrated is only causing mold and mildew behind the old sealant. Good air circulation for a couple of days augmented with a fan will help dry it out.

IMO only silicone caulk belongs in a bathtub or shower area. Any other caulk will either soften and leak, or dry hard and peel off when the area flexes.

007noob: Sorry I'm late to the party got busy. I've been in this business for 40+ yrs, and had really good luck with color matched 100% silicone. I learned from an old guy years ago to run my bead a little over sized, then use the round end of a plastic spoon to get a uniform bead. Let it dry and blade off the squeeze out. As chandler48 advised, make absolutely sure the area is DRY. The single edge razor blade makes quick work of squeeze, and gives you a proffesional uniform bead. FYI guys n gals, IMO the spoon makes glass block look exceptional !! Better than a finger.....