IF you read the Guide, then you would know that they would eventually float back up to the surface and have a chance of infecting you. So while they can't technically swim, they can float and be just as dangerous...

BUT the guide also says that they cannot climb most things, and while they may be able to form a zombie ladder, this in an ocean would be impossible because of the currents and "motion of the ocean" for lack of a better phrase.

Indeed they can not climb, but no place is safe, only safer. And unless this boat is small enough for me, and the few people I want with me during a zombie apocalypse, where will I be able to grow food to keep myself alive. If the boat is big enough for food growing, where am I gonna find the people to help protect the boat from marauders? Either way yes a boat is one of the safest places you can be as long as you don't get lazy and make sure every floating body is completely dead by shooting it in the head, I'd rather take my chances else where. Also humans are gonna flock to the ports in hopes of putting out to sea, it would be a death trap unless you are already living on a boat.

You don't actually have to shoot the zombie, a blow strong enough with a blade, or blunt object is sufficient for killing a zombie, using a rifle or pistol is pretty much begging for all the zombies in your area to come and say hi, a silencer will help this but it does not mean that it will be dead silent it will still make sound just on a drastically reduced amount.

That is true IF you are on a boat, and that is if you have a large boat, those who have smaller boats may find, from the guide, the shaolin spade a viable weapon on eliminating the threat, and if you are on the boat I am assuming you have means to leave the immediate area, as well as if the zombie's body has bloated enough to reach a point that it can float its body has died almost far enough to not even move.

Even the majority of small boats would be too high up for most melee weapons. Yes a shaolin spade is long, but probably not gonna reach a zombie in the water unless you are in a row boat. And yes you could leaves the area, but I wouldn't unless there were a few hundred bodies floating there. Though it might take a year or so for a zombie to be able to float up to the surface again, I'd rather take the precaution of eliminating it myself than just assuming it is not able to bite me, or anything else.

Don't get me wrong the only good body's are the bodies with a bashed in/round through the skull. but when it comes to locations to be safer I would rather be on land and know that if I have a zombie outbreak in my group i dont have to hope that the life boats are ready.

So at least we can agree then. Land is usually a better, more viable, option for the average Joe? IF you go up the first comment you responded to of mine, you will see I advocate staying away from ports, due to the high demand that they will bring in case of a zombie apocalypse.

I did read that and do agree, and unless your a professional sea-goer and are on the oceans/sea when the outbreak would occur I would agree with you stay away from ports, as well as any "security" set up by, the military, police, or any other government organization. as anyone who has read the guide will know that going to it would almost guarantee death. If there was a small town in which has their shit together and are prepared with a fence and a trained force for this situation that can easily be self-sustained would be the best situation like in the novel "Thunder and Ashes

i believe i can contribute to this,
wile a boat would be a viable option, you would need enough fuel and weapons and food to be able to sustain this as the main problem with boasts is that the main protection (water) makes it impractical for long trips, as restocking eliminates a large portion of this protection,
instead i would suggest clear raised ground, prefferably with a wall;pit or other un-manned protection surrounding it i would suggest a wall with a pit outside.
and if a raised platform could be placed on the inside of said wall you could use ranged/long melee weapons to protect your fortress even longer.
you could also place sleeping/storage/other rooms underground allowing maximum posssible farm area.