The Tam Coc boat ride is the most popular in Ninh Binh, because one of the entry points is steps from Tam Coc’s main corner, where restaurants, hotels, minimarts etc. converge. It’s lovely, but shorter and not as interesting as the Trang An boat tour. Tam Coc is also known for having much more aggressive guides, who will essentially refuse to bring you back to shore unless you give them a $20 or $30ish tip on top of the ticket price. The ‘galaxy grotto’ is awful in my opinion; they’ve lit the cave with brightly colored lights, many flashing or swirling.