Your eyes are designed to work better underwater than a normal dino, but the T-rex DNA screwed up your specialized version of underwater navigation. Hence why you can get several versions of eye upgrade or ultrasound like a dolphin in misc mutations. Otherwise you are still a very good swimmer, but nightime swimming and deep water diving are likely to get you lost.[X] Examine the fish more
we should have the spinosaurs ability to detect underwater movement, (kind of like a sharks ability to feel electrical signals, but more based on movement in the water so the spoons can catch fish.)