Ground and Neutral Line Connection

If you are talking about a shore connection the ground will be joined to the neutral at the main breaker panel fed by grid power. Normally the power company pole has it's neutral grounded at the pole then where the power enters the house or business the neutral is again grounded with a driven rod right below the meter. Then the first main breaker panel will also have the ground and neutral joined. From that point onwards the ground and neutral are separated. If you are powering a boat with a shore power connector the ground and neutral will be separated and the AC wiring on the boat will also have the ground and neutrals separated. This will provide the safest arrangement.

http://en.wikipedia.org/wiki/Earthing_system

no i'm not talking about shore side.i get 3 phase and ground from marinas . And my shore power galvanic isolated. The secondary side of shore power ( yacht side ) provides 3 phase and ground.

On the other hand , the issue is inside the mainswitchboard ground and neutral bus bars are connected with a cable and breakers are 1-pole . As far as i consider , if the grounding point of the boat is loosen or grounding system weaken anyhow , people may get shocked .

However , in my previous boats neutral and ground were seperated . And the breakers ar 2-pole. So that's a megayacht , it must be safe.