Designing Kitchens and Bathrooms - tile falling off the walls

I was taking a shower and a tile started to fall off the wall. So I started looking around and noticed that all the drywall around the shower is soaked. I went into my basement underneath the tub and noticed that I had a puddle on the floor from all the water. I had a plumber out and it's not plumbing problem he said I need to replace all the drywall. My question is I wanted to redo the bathroom anyway with an acrylic seamless tub, should I take all the tile off and rip the drywall out and replace it? and if so should I just use regular drywall or do I have to use someother type of drywall or cement because it's the bathroom?

You said you want a seamless tub but you didn't mention anything about a surround. Either way you should remove all the drywall that is damaged or needs to be removed to install your tub. If you are planing to redo a tile surround then you will need to also tear off the drywall and install cement board where the tile will go. Any place you intend to have just a smooth, painted wall, you should install moisture resistant drywall. Moisture resistant drywall is just that. Moisture resistant. It is not intended to get wet a lot.

There are differing opinions on the use of moisture resistant drywall, often called greenboard because of it's paper color. In my area it is still available but no longer required by code.

While no drywall is designed to get wet, regular drywall when properly primed and painted is just fine in a bathroom. There is a product sold as paperless drywall that is supposed to be mold resistant but I haven't used it.