To access Waterloop Station, the red switches strewn about must be pressed in the right order. Travel in a perfectly straight line from each raised signpost to find the next correct switch, beginning from the one at Lakeside.
Diveal Island
Here at the lake's northwest corner are plenty of roaming Diveal. It is the first opportunity to acquire the Diveal Swim ability.
Elemental Altar
The elemental Altar of Water is far to the west, directly below Diveal Island on the map. Approaching it with Felix during the Don't You Want Me quest leads to a fight against Scubalveal (Scubalrus and Diveal fused)
Cave
A cave will emerge on an island far south, after a hidden green switch in Upper Path is pressed. Inside is a cache with a Rogue Fusion.
