Evolution Square recently made a video about creative ways to use the lagoons, and one of them is a really good way to incorporate underwater tunnels for guests and tour vehicles.
Source: https://www.youtube.com/watch?v=mJlZQJfya6U
With being able to lower the terrain surrounding the lagoon so far, it would be easy to make an entrance attachment for the wall. It doesn't even have to be that big, just a pair of sliding doors that open to a tunnel the same width as a wide path and the vehicle/gyrosphere tracks. Then you place the tunnel along the bottom of the lagoon and connect it to an exit door the same way. This would also allow a way for unhappy marine reptiles to pose a threat to guests, they can attack and damage the tunnel requiring a Ranger team to go repair it similar to how they repair a tour vehicle attraction.
With being able to lower the terrain surrounding the lagoon so far, it would be easy to make an entrance attachment for the wall. It doesn't even have to be that big, just a pair of sliding doors that open to a tunnel the same width as a wide path and the vehicle/gyrosphere tracks. Then you place the tunnel along the bottom of the lagoon and connect it to an exit door the same way. This would also allow a way for unhappy marine reptiles to pose a threat to guests, they can attack and damage the tunnel requiring a Ranger team to go repair it similar to how they repair a tour vehicle attraction.