Bahia Maimon is a bay, not really a town. There is a little hamlet, that's it.
However, the bay is beautiful so if you love nature this is a good place.
I guess you will be staying at either the Riu Mambo or the Riu Merengue. Both have discos and entertainment and that is all you are going to find in Bahia Maimon. As for activities there are all the classic watersports as well as your usual twisting by the pool (water aerobics etc.)
On the other side, you are not that far from Puerto Plata (about 15 minutes in a taxi) and there is enough action to satisfy everyone there. Just beware that if you go every day the taxi fare will add up in the end. I think you will find a guagua at the main road (at least you will from Cofresi which is the next town on the way to Puerto Plata). Guaguas (shared taxis on regular routes) are very cheap, uncomfortable and fun.
Remember to leave your resort and go exploring. Both Riu hotels are nice but you didn't go all the way to the Caribbean just to see what you could see in Mallorca or the Canary Islands, did you?
Regards,
Susanne