This island is huge, about 1,000 miles by 500 miles. Each hex is TEN miles. You can generally explore one or two hexes a day.
A navigator makes a daily Wisdom (Survival) check to avoid getting lost. You can hire a guide, especially if you want to go someplace and you're not sure where it is.
Characters moving at a normal pace can travel 1 hex per day on foot through coastal, jungle, mountain, swamp, or wasteland terrain. They can travel 2 hexes per day if they're traveling by canoe on a river or lake. The rate of travel up or down river is the same; the rivers are so sluggish that current is almost imperceptible. Without canoes, the normal rate of travel along a river is the same as through the surrounding terrain. Canoes move 1 hex per day through swamp.
If characters move at a fast pace, the easiest way to deal with their progress is to roll a d4. On a roll of 3 or 4, they advance 1 additional hex that day. Characters moving at a fast pace take a–5 penalty to their passive Wisdom (Perception) scores, making them more likely to miss clues and walk into ambushes.
If characters set a slow pace, roll a d4. On a roll of 1 or 2, they advance 1 fewer hex that day (in other words, 1 hex by canoe or none by foot). On any other result, their caution is rewarded, and they travel the same distance as a group moving at a normal pace. Characters moving at a slow pace can move stealthily. As long as they're not in the open, they can try to surprise or sneak by other creatures they encounter.