The Cliff Plateau Isles comprise a tight cluster of smaller isles grouped around a slightly larger one. You can’t reach the top of the larger isle without traveling through a Secret Cave. Enter it via the hole on one of the smaller isles.
Sea Platform
Sail to the single Sea Platform and climb its ladder. A chest sitting on top contains a minor reward.
Treasure Chart #25 (via Secret Cave)
The only way to traverse the Cliff Plateau Isles and reach the largest isle is through the Secret Cave that you enter via the hole on one of the smaller isles. Start by walking up the slope of the first of the four smaller isles, then hop across each one until you come to the Secret Cave entry. Fall into the hole to enter it.
This cavern has a few obstacles for you to overcome before you can reach the other side. First, manipulate the circular platforms so you can cross them and reach the higher area of the cavern. Use the Deku Leaf to spin the platforms or to glide across them.
Once past the circular platforms, make your way around a wall of thorns that sprouts from the ground when you get close. Move slowly to avoid charging into them. Defeat the Boko Baba near the two tree stumps. It leaves a Baba Bud behind. Use the Baba Bud to reach the flat tops of two nearby tree stumps, and then carefully hang and drop to the chest below. Open the chest to get a Joy Pendant.
Once you open the chest, several (but not all) of the walls of thorns disappear, allowing you access to the Deku Pod again. Use this to reach the tops of the tree stumps, and then look for a wooden gate nearby. Use a Fire Arrow to burn away the wooden gate, revealing a ledge and an alternate exit from this Secret Cave.
Use the Deku Leaf to glide from the closest tree stump to the ledge. Walk into the shaft of light, and you appear on top of the largest Cliff Plateau Isle.
Here you find a Blue ChuChu, a Withered Deku Tree, and a chest containing Treasure Chart #25. You must travel through this Secret Cave again to water the eight Withered Deku Trees.
Triforce Shard #8 (via Triforce Chart #3)
After you find, open, and pay Tingle 398 Rupees to decipher Triforce Chart #3 (found in the wreckage of the golden Warship near Needle Rock Isle [A5]), you can pull a chest from the Great Sea near the Cliff Plateau Isles. The chest contains Triforce Shard #8.