Is it fiberglass? If so, check at boat place for repair kit for fiberglass. Probably cheaper for you to do the repair than have an RV shop or boat shop do the repair. Seems like a pretty small hole to fix, so go for it.
Good luck and welcome to the forum.
Find a glue that melts the plastic, maybe ABS or PVC cement from the plumbing department of the lumber yard. Find a bit of plastic of a similar kind, maybe from a dryer vent for instance, cut a patch and glue it on.
If it needs to be curved soften the plastic with repeated applications of the cement for a few minutes before applying to the tub. Give it a couple of days to dry and harden up again. :approve:
harbor freight sells a plastic welding kit,not sure of the price but its well worth it,you can weld ABS and polyethelene plastic with it,i have a pro model that i use to repair plastic and rubber motorcycle and car parts.fiberglass wont stick to plastic,some 2 part expoxies will if the area is roughed up enough,but its just a temp fix.
I have found a good and inexpensive meathod to repair plastic tubs, jsut take some coarse emory cloth and scuff the surface, then get some fiberglass matting, and soak small patches with ABS Cement, layer them a couple of times over the hole, let that dry and then a little paint from a rattle can and you are repaired!