First you need to understand that in the USA there are two ways to "register" a boat.
One method is to register a boat with the US Coast Guard part of the federal government
. This type of registration
is called documentation
is only allowed for US citizens or US corporations but also is not allowed or needed for small boats. For these two reasons federal documentation wouldn't make sense for you and your jet skis.
The second method it to register a boat with an individual state. All US states have a process to register the boat and, as far as I know, no states restrict this process to US citizens. State registration is usually easy, cheap
and has no residency or citizenship restrictions so this would be the best method for you. You also can do this as an individual so would not have to set up a Delaware corporation unless you need to do this for some other ownership
or tax reasons.
Information for Delaware state boat registration at this link.
Delaware Boat Registration Information
A couple of other comments. If you are purchasing
the jet skis in the US you will probably have to pay state sales tax (similar to VAT but usually only 5-7%), even if you buy them used. Also, unless you want to have Delaware registration for some reason you can register in almost any state you choose. However, if you will be keeping the jet skis in the US you should register them in the state where they will be kept. Most states will require you to do this anyway if they are kept and used in that state.
Cost for state registration is also cheap
. Figure USD $50-$150 depending on the state.