Do NOT go to the posted coordinates. Do NOT get your kayak out of the shed. You will NOT need to swim.
This is a Bonus Cache which you can look for after you do an Adventure Lab!
Be sure you have the Adventure Lab app on your smart phone.
Look for the adventure Wherefore ART Thou, Marco?
( HINT: You will be exploring places on Marco Island.)
When you have completed the 5 stages, you will see the coordinates
for the final Bonus Cache.
Have fun!