If you are in Alibaug and you want to experience authentic coastal food, in budget, you may head towards Sanman Hotel, on Israel lane. A fish thali is a specialty there. It is the simplest and quickest of available meals which you can enjoy. A part from that lobsters, crabs, bombil fry, sukka(dry) prawns are also there in the menu.
If the popularity of sea-food is indicating to you that there would be fewer options for the vegetarians, then you are wrong. The vegetable and fruit markets are vibrant in Alibaug. Some local vegetarian dishes are Phansachi Bhaji(jackfruit curry), Kajuchi usal(cashew curry), the most readily available urad dal, amboli(puri), bhakri(roti made of rice) and last but not the least papad. The simplicity of the food does not make it less special and tasty. A part from this south-indian cuisine is also available almost everywhere.
If you wish to enjoy fine dining then Aparanta, a multi-cuisine restaurant is a good place to go. It is always recommended to stay in Homestay in Alibaug near beach to get full experience of local food and culture