I bought a great boat and...

[Rolig Loon]

I assume you mean that you have been sailing around for a while and then stand up, and the boat disappears.  That's likely to happen if you sail into private waters where object entry is not allowed. As long as you are sitting, linked to the boat, the boat can stay rezzed.  As soon as you stand up, though, the boat is violating the local Object Entry rule.  You shouldn't have any trouble if you stay in public waters like the Blake Sea.

[Rolig Loon]

I assume you mean that you have been sailing around for a while and then stand up, and the boat disappears.  That's likely to happen if you sail into private waters where object entry is not allowed. As long as you are sitting, linked to the boat, the boat can stay rezzed.  As soon as you stand up, though, the boat is violating the local Object Entry rule.  You shouldn't have any trouble if you stay in public waters like the Blake Sea.

[sven Homewood]

You found a landfeature called “Autoreturn“. Most public areas have that set to 5 or 10 minutes to advoid objectlittering on the parcel (and make it less intresting for griefers). LL has it turned on on their protected land. The 'private' estates as well. On the opposite they have build turned on or rezz areas. As long you sit, the boat stays, if you stand up, the boat gets returned to your inventory when the time of the autoreturn has reached.