The best way to my opinion to get here is by car.
The location of the city is on the main route from Haifa-Tel Aviv so you can stop here for a while and continue your way.
To go to the Marina area you should get down on the boat junction (Ha'sira) and this is Herzliya Pituach.
If you want to use train you can get to the stop close to the 7 stars mall.
I think it is not the best location if you want to go to the marina because from there you must take a taxi or walk for 30 minutes.
From Tel Aviv it will take something like 10-15 minutes and it will cost you 7.5 nis.
rom Haifa it will take something like an hour and it will cost you 25 nis.
The train that goes from Tel Aviv to the north stops at Herzeliya as well. so thats one comfortable way to arrive.