First you can drive all the ground rods you want to but it will do nothing to remove the “trickle shock” hazard between the shore and the water. There is not a motel somewhere underground that electrons retreat to nor is there some kind of electron party that take place underground. Every one of those little electrons are doing their best to return to their source and the improper installation is forcing them to seek a path back through earth.
The size of the conductors supplying the dock disconnect will be determined by the load served. To size these conductors everything being served will need to be calculated. Without the size of the pump motor, lift motor and other items it is impossible to say what size these conductors need to be.
If 240 volts is needed for items such as the water pump and boat lift then a four conductor feeder will need to be installed to the dock disconnect. ALL conductors supplying the dock will need to be insulated something that won’t be found using a UF cable.
The disconnect for the dock will need to have its own grounding electrode system established with the neutral being isolated from the insulated equipment grounding conductor. This equipment grounding conductor should be size 12 or larger.
An Equipotential Plane will need to be installed at this dock panel that reaches out no less than three feet in all directions.
Everything at the dock will need Ground Fault Circuit protection. I recommend GFCI breakers in the dock panel.
This code compliant installation is the only way to stop the “trickle shock”
Remember that people die every year from shocks received from dock electrical power.