Find the Half Pendant of Aquatic Agility and the Half Pendant of Aquatic Endurance. Speak with the residents of Moonglade to learn clues as to where these items may be located. Form the Pendant of the Sea Lion from the two pendant halves. You need to be in proximity of the Shrine of Remulos to do this. Bring the joined pendant to Dendrite Starblaze in the village of Nighthaven, Moonglade.
For the second trial, you'll need the two halves that make the Pendant of the Sea Lion. One half draws power from the agility of the sea lion aspect, gliding through water; the other draws power from the incredible endurance of the sea lion aspect. Druids draw on both these traits equally to embody the aspect of their aquatic form.
Speak with the locals of Moonglade to learn where the parts may lie, and bring both here to join them together. Once formed, take the pendant to Dendrite Starblaze.