Mahahual is an interesting place South of Yucatan peninsula and almost on the border with Belize. It's a super small beach village, but in dry season starting from November it is visited by about 8,000 people per week which seems unbelievable for such a tiny place. The thing is that most of these people don't stay overnight, they come on huge mostly US cruise ships that dock in Mahahual about 4 times a week, spend a day on the beach drinking margaritas and eating seafood and by 5pm they are all gone back to their cruise ships. In wet season from around May till October - it's only about 2 cruise ships per month that come here.
This makes it a really nice destination in August when we were there - it's quiet, chill, very few tourists, the village kind of becomes what it originally was - just a tiny fishing village. That's when you can enjoy it the most. Wet season only means that there might be occasionally some rain in the afternoon.
The village is so small that you'll find most of the things along the beach - cafes, lounges, restaurants, hotels, couple of shops and snorkeling/diving shops. Accommodation and restaurants are designed to cater for those package tourists that come in dry season, so it's not exactly cheap, but you can still find good options. We found a 100% Agave hostel in the very center 2 minutes away from the beach - it cost $18 per night, but it was very basic, expect to pay about $35 for a good place. When staying by the sea it would be a shame not to eat seafood - it's going to be about $8-15 a plate (fish any style, seafood plates, etc.) You can also go for eateries on the second row street from the beach - these are significantly cheaper and are serving more traditional Mexican dishes.
To save money a much better option is to buy your fish and seafood directly from the fisherman that come onshore in the early morning and at about 4pm - just ask around where on the beach to expect them and you can buy all sorts of fresh catch for about $5-8 per kg (they'll clean and gut them for you) And in the evening you can grill it right on the beach by making a fire or arranging for a grill with some locals which is what we did.
Locals in Mahahual deserve special mention - everyone who lives and works there are super friendly and nice, if you don't behave like an arrogant tourist you'll be treated like a friend. People will invite you to spend time with them, to have food together, to have a chat, etc. We met a really nice tattoo artist girl who just calls herself a hippie, arranged to buy some fish from the fishermen together and arranged with a random local to come to his backyard to use the grill for the fish. Pretty awesome BBQ we had!
There are a couple of late night places where the locals go to party - a bar in Casitas (about 20 min walk from the beach) and Bodeguita - right across the 100% Agave hostel (2nd street from the beach) It's cool to check those out and meet some more locals.
Mahahual is famous for its snorkeling as the reef which is one of the last alive reefs left out there is just about 100-200m from the shore and goes all the way South to Belize and Honduras. Take a snorkeling tour (about $16-20 per person) and they'll bring you to better and farther spots by boat.
Even though the village gets crazy daily tourists from cruise ships in dry season it's generally quite remote and much less visited than the beach towns up North towards Cancun - so if you're coming from the North you'll experience a nice break from tons and tons of tourists, and if you're coming from the South and heading North - know that these are the most remote and least visited beaches you can get on the Caribbean coast of Mexico, you won't get that moving up North.
If you'd like to experience even more remote and untouched beaches - you can go to Xcalak south of Mahahual - the Southernmost village before Belize border. It's an even smaller fishermen village, but it has a couple of guest houses and cabanas (bungalows) - those are not cheap (about $40-60), but worth the money considering the remoteness and unspoiled beaches. To do that you can take taxis all the way to Xcalak or you can come by a rented car which is what most people going there do. As the beaches in Mexico are all public and free to be used by anyone - you can just go to some remote beach between Mahahual and Xcalak, put up your tent under a palm tree and enjoy the beach life with no people around.
Choose the wet season and you'll enjoy Mahahual a lot!