When you have a lake house over the water (entirely), is there any necessity to pull a flood determination and have the borrowers sign the notice? The structure is obviously uninsurable.

The requirement is if you make increase renew or extend a loan secured by a structure, you have to make a determination of whether or not the structure is located in a flood zone.. That requires you to document it on the required form. If it is in an SFHA, then you have to give them a notice telling them if insurance is available. The insurability of the structure base don type is not a consideration in teh determination and notice requirements.

So yes, you still need a determination and the notice.

Agreed. There is no exception for the determination/notice requirement.