Kelp uses holdfast instead of roots. These grab onto the ground of the surface it's on. Moss in the water holds onto rocks so they don't flow away with the tide and waves. Also, some seaweeds are leathery that helps them from getting torn.
With some redneck Engineering, we have found a way to make comfortable, tough, and helpful climbing boots.
When you hike the bottom of the shoes grip the ground beneath you. That gives you more grip and you can climb to higher heights. Plus with the moss based souls any water that were to get into you boots goes into the souls.