Oil Rig Pipeline
I think it would be an interesting concept to make a permanent pipeline from an excisting oil rig to your island. It would take time ofcourse, maybe even need to upgrade the boat in a certain, but could be an interesting mechanic in the end.
When the oil rig is dry it could maybe even be converted to a hydrogen plant and use the excisting pipeline for hydrogen transport. This option is for example currently being looked at in the Netherlands in an attempt to make a large scale hydrogen production chain.