Snorkeling Trunk Bay is definitely the most well-known on St John. The beach is beautiful and so are the turquoise waters. Though it is not dense, there is some coral life to see here and a decent number of fish, making the snorkeling good, but not great.
Note: This page is a sample from our popular St John Snorkeling Guide eBook available here.
Offshore near the right end of the beach is an island called Trunk Cay, famous for its underwater snorkeling trail. When we visited, the signs for the trail were overgrown and unreadable, though we assume they clean them periodically. Because the trail is close to shore and well used, there is not much of the coral and sea life left that is being described on the plaques. To really see anything, you need to swim well past the end of the snorkel trail. Read more below.
Trunk Bay and Trunk Cay are exposed to winds coming from the north, including the northeast. Also, if the winds are strong from the east it will be too rough to swim and the currents will be strong on the east and north sides of the island. So, consider visiting some other spot if the winds are up from those directions.
In addition to folks visiting St. John, Trunk Bay Beach is the destination of many cruise ship visitors coming over from St. Thomas, so the beach and parking area are usually crowded.
It is the only national park beach with an entry fee, $4 when we visited. The beach offers full facilities, including lifeguards.
The water entrance for snorkeling Trunk Bay is sandy. We noticed that the beach is slightly steep which means you need to keep an eye out for breaking waves.
There are three basic areas you can explore snorkeling Trunk Bay.
On the far right side of the beach you can swim along the rocks. There are a few corals, sponges and fish to see here. It gets less healthy the farther out you go toward the point, and the visibility goes down too.
The island, Trunk Cay, has snorkeling all the way around it. You will see signs on the beach warning that if you swim around the island the lifeguards cannot see you. This is of course at your own risk. Make sure it is calm enough to even attempt it. The approximate distance around the island is 2000 feet, not a short swim. So be sure you are up for it. If not, stay on the left (looking from the beach) side of the island.
Snorkeling Trunk Bay along the right side of the island, it is mostly rocks and a good number of fish. As you approach the far point of the island, it gets deeper, and you start to see more corals. For us the visibility improved and was very good near the point.
As you round the point and start heading back to shore on the left side of the island the bottom drops off and is rocky, down to 20 feet in depth. The topography is fairly interesting. Along the left side, just after the point, you will find a nice patch of healthier soft corals and some hard corals. There are less fish on this side, but many sponges and tunicates. This is where the best corals are for snorkeling Trunk Bay. This side of the island is generally much busier with other snorkelers because it is more protected from the east winds and waves.
As you get closer to shore you will start to see the underwater trail plaques.
You can also snorkel the far left side of the beach, along the rocky shore, heading for Jumbie Beach. Be careful here as this area is more exposed to waves and can have some current. Unfortunately, next to shore you will find a dead Elkhorn Coral reef that now has very sparse mostly unhealthy corals, and we saw few fish. Slightly offshore there are patch reefs of Lobed Star Coral, most of which are dead too.
Overall we experienced decent visibility, with some areas being very good. The depths for snorkeling Trunk Bay ranged from 1-20 feet.
We found a generally unhealthy reef with some areas of live corals, including nice soft corals, sea plumes, sea rods, etc. We saw many sea fans too but most looked unhealthy. There were many groupers, including Rock Hinds and Coneys and large Yellowtail Snappers obviously begging for a handout. We also encountered large schools of jacks swimming by quickly.
Coral - sparse and in small amounts:
This park has full facilities. There are bathrooms, shower rooms and foot showers. There are many picnic tables in the shade with barbecues you can use and trash cans. There is a beach and snorkel gear rental place, a small store with basics, and a little grill snack shop. On the beach there are lifeguards.