This activity was part of my 3 day trip to Bintan - I booked this activity via Klook, which comes with pick up service and even meal options!
As a chill day 1 activity, I booked the Mangrove Pontoon Night Tour, which could not get any more chill - All you do is sit down at stare into the darkness while listening to the boat's rumbling engine and your guide's mini lessons on the mangrove and its fireflies (More on that).
When we arrived at Treasure Bay Bintan, we simply had to wait at Chill Cove @ Treasure Bay Bintan for the operator to come pick us up.

Cute and vintage-looking vehicle parked where we were waiting for the tour to start
We were well on our way after a short buggy ride to the pontoon point. Night has fallen and we were given life jackets prior to boarding, then off we go!
When we went, there were no other participants on the tour, so it became a private tour for us. Our guide was entertaining and taught us how to catch fireflies, before effortlessly catching one with his bare hands. Opening up a little, we could see the little glow through the gap in his hands. In the darkness, the fireflies were just like little moving flashlights in the background. I caught one myself (gently and without killing it) before releasing it back to join its friends.
As the pontoon boat made its way back to the start point, I laid down on the pontoon and stared up into the night sky, which felt liberating because I could see the stars clearly from where I was.
Be sure to Apply repellant generously prior to the tour if you don't want to be a walking buffet for the mozzies. We were NOT prepared for that, but fortunately our boat operators had some to spare.
Overall, I'd recommend this activity if you have an hour or two to spare while on your holiday and want an activity that does not require much walking and effort.