There are black pearl nodes in the deep water zone on fjordur. The entrance is at about 56 lat 17 long where the hexagon formation are. Swim down.

This area is filled with mosassaurs and squid including alphas. I suggest either a fast mount with good weight, or tame a crab. It’s slower but plenty of weight and the baddies completely ignore the crab. Go grab some pearls and tame a squid :)