I booked this place from europe over expedia but I would not do it again. We paid more than 50 Euro per night and you can have it much cheaper in La Crucecita. The plus is definitly the location in Santa Cruz, just a little walk around the Marina and you are at Santa Cruz beach, cam enjoy the sun, a cool beer or some food in one of the numerous restaurants. We actually liked the less-touristic center of La Crucecita better. And from there a Cab to the beach is also just 20 Pesos...
To the hotel. We had a huge flatscreen TV, every day new towels and a enormous bed. Fantastic. In the bathroom we got every day new towels, soap, creme and bottled water. But also there was a little but of mold. The walls are made of concrete but netherless we heard are neighbours. Also we came off the season, so they tried to fix the pool area with some paintings, exfoliation was obvious.
The breakfast was included, when the waiter showed us the menu I decided to take a "Marina omelette"...When we left they asked us to pay 50 Pesos because this was apperently not included... After complaining at the front desk the hotel staff solved the problem, but the bad first impact stayed in my mind. The next days we had hot cakes or scrambled eggs, now there was no problem with extra payments...
So, if you want to stay close to the beach, this is a good place. I recommend a more simple place in La Crucecita. There you can enjoy the real Mexican life and Taxis bring you to the beaches for almost nothing. And, no tour operated hunt you when you leave your hotel to see something. This was also annoying.

My parents, who are in their 60's, wanted to spend the New Year by the beach. We settled for Huatulco as we were touring Chiapas and Oaxaca and it was the logical thing to do. We had been to Huatulco several times before, usually at Las Brisas in Tangolunda Bay, but this year we booked so late and through a travel agency and the price at Las Brisas was prohibitive!
So the travel agent recomended Marina Resort, gave us a good price (no breakfast included though) and off we went. I guess not a lot of people drive to Huatulco, but if you do, the hotel provides free parking. The parking lot however is tiny, and sometimes you have to leave your car on the side road, which is full of cars. Also, it is a two way street, so it is not that easy to get in or out. In any case, it is safe to leave the car there, right by the marina.
The location is good, and they advertise a "beach club", which as someone else mentioned, is there physically but not very enticing when you can go to Chahué or other beaches close by.
Some of the staff does not speak English, and while this was not a problem for us, it might be inconvenient. They are very helpful, for example they changed our room because when we arrived we were assigned a room in the 4th floor. My mother has some problems walking, so they gave us room B instead, really close to the hotel lobby. There are no elevators, so it might be a bit inconvenient for people with mobility issues, as you have to go up stairs to get anywhere.
The pools are ok, but there aren't many areas to sit down, so you might want to go there early, to grab one.
We encountered some problems: when we arrived in our room, one of the lights was not working. We reported it, but it took them a while to get it working. The T.V. was not working properly, but if you go to a beach hotel, this is probably not important. We asked for an iron, and it took one day for them to locate one. And then we asked for our beach towels, but they didn't have any, for a day. When we arrived, we also did not have towels in the room, nor toilet paper. We had to ask for both and again, it took a while for them to get them to us.
The restaurant is not that expensive, and the food is your basic hotel fare, nothing too special about it.
But it is a basic hotel, in a good location and at a discount, like we got it, it was ok for the trip.

After reading the other reviews i must disagree. This happen to be on of my best experience ever. And I have stayed at five star hotels before. Yet, due to the economy I could not spend that amount of cash. After staying at the Marina Resort I realized that I wasted a lot of money staying at these Five Star Hotels. The only thing that I did not like is that coursty they had for a type of guest that came and did not want the music too loud. However before they arrived we were catered to like there was no tomorrow. Whatever the other people felt I can reassure you that there was no ant and that they do serve breakfast. You just have to get your ticket in the morning. Oh, and for you eco-friendly people, this hotel is rated very high for that.

Final thought, for the nights I was in my room a LCD tv would have been nice. But I had too much fun.

Very nice hotel, good price, nice view, nice location, large room, clean. Breakfast was included . Nice and helpful staff
But...
We stayed 5 days, had NO hot water for 4 days, the heater was rotten and dead and had to be replaced (what we were told). It was never replaced and we still got very hot water but only the very last night. !!!
The swimming pools (all 3 of them) could have their filters running longer.