fresh water storage on 406

70 gallons is just ridiculous on a boat that size. For the Bahamas you ll need a water maker, www.seawaterpro.com has units for about $3k. We have one as a back up to our primary and it’s pretty good.

Pretty much any boat can make it to The Bahamas especially in summer. In winter you ll have to pick the right weather windows especially if going further in like to the Exumas.

besides water refrigeration especially freezer space can be a challenge for the Bahamas.

Well,,,
Are you really traveling far from a dock with water?

I don't think you will have the fuel to travel far between fuel pumps. Most fuel docks offer water.
In the islands they may charge for water but most don't if you purchase fuel.

In my youth, in the islands, I jumped over with a bar of soap and a toothbrush.
Before water bottles,, but about one of today's water bottles was used to rinse my eyes and private parts.
In the islands, short hair is preferred anyway because of the heat. So that is not an issue.

Utensils also get washed on the swim platform.

If your going to the islands in a 40 footer for more than a weekend, away from the marinas every night, wilderness survival training and practical sense will be required.