Wood under bathtub

Hi Stacie,a photo would give more clarity as to what the purpose of the particular piece of wood is. If it isn't a structural part of the surround that keeps the bath secure you can just get a little L shaped bracket from the local hardware store and secure it with a couple of small screws. most baths have a metal frame front and back with extendable "feet" to level it out and this is what takes the weight. I wouldnt worry too much about it but if unsure get someone to have a look. Dont atempt anything that may cause harm to yourself or damage to the bath. If in doubt ask a professional.

The timber secured to the underside of the bath is there to reinforce the bottom. It should be secure as the weight of the water and the person in it may cause the acrylic to crack/break and you will have bath water everywhere.

I agree a picture would be helpful but the most important thing is that the adjustable feet are on a secure base.