Laguna Grande is one of three bio bays in Puerto Rico, all with the same type of dinoflaggelate, and among about a dozen such sites worldwide. Laguana Grande is on the island’s northeast side, near Fajardo. While our guide said it has the same brightness and concentration of organisms as Puerto Mosquito, off nearby Vieques island (a 75-minute boat ride), die-hards disagree, saying that that Puerto Mosquito is better. If you want to go to that bio bay, you’ll need to stay overnight on Vieques unless you have your own transportation back. There, you’ll take an electric boat (thereby eliminating our mangrove paddling adventure).

The other Puerto Rico bio bay is La Parguera, in the southwest part of the main island. From all accounts, the dinoflaggelate concentration there is as much as 90 percent lower, due to a damaged ecosystem.

Alas, it was time to paddle back. I thought the return trip would be easier, since no groups were making their way into the lagoon at 9:45 p.m. To stay together, we played a game of telephone, with the front of the group passing back messages to the back. The most difficult message to follow was “slow down.” But by the time it got to us, that really meant “stop.” That’s hard to do when paddling at a good pace in 25 feet of water. I floated past several others boats, with Dori whacking them with her paddle. I apologized profusely. With a child in my boat, and my self-deprecating attitude, most of our group was quite forgiving.

Though I felt like a terrible kayaker, my friend Rochelle was worse. For each time Dori and I paddled into the mangroves, Rochelle and her daughter crashed an additional two times. Her daughter eventually just put her arms protectively in front of her face to avoid any branches.

Back on land, our guide asked how many of us went into the mangroves. Everyone’s hand went up. I didn’t feel so bad after all.

While the glowing dinoflaggelates were a trip highlight, the adventure of kayaking in the dark mangroves is what we still talk about.