Hi XXXXXXXXXXX;
There are appliques made by 3-M that you can purchase at any hardware store or home improvement center. Just tell the sales associate what you wish to do and dont buy the cheapo ones. They always curl up on the edges. The 3-M ones you simply peel the paper backing off of and apply them to the bottom surface of the tub. They are made of good quality rubber and the glue they use is strong enough to take a layer of gel coat off with it if you try to remove them. Well at least it seems like that if your the one tasked to get them off.
Please post any other concerns here.
Best, THS
Jack of all trades Master of a few.
#1 Home Improvement Expert. Over 30 years experience in construction, and home repairs