A Tidewater is when a family is purchasing a home using a VA home loan and the appraiser sees that the homes value might not be supported by the comparable sales they are finding. They will then reach out to a designated point of contact which is typically the lender processor but can be the agent as well. They will let the point of contacted about the situation and they will request additional comparable sales or addition info to support the new purchase price.

In the VA handbook it reads…

"A major change in VA’s policy regarding interaction between VA Fee Appraisers and other program participants was introduced in 2003. In brief summary, the Tidewater procedure allows an opportunity for a designated “Point of Contact” to provide market evidence for the appraiser’s consideration prior to establishing the final URAR value. The appraiser initiates the procedure by alerting the Contact person that the appraised value appears likely to come in under the sales price. The appraiser should not discuss the appraisal contents except to explain that the comparable located by the appraiser do not adequately support the sales price. The Contact person then has two business days to provide additional sales information in support of the sales price. Verification of closed sales is required. (Pending sales may be offered, but should only be used to support time adjustments.)
All attempts to communicate with the designated Point of Contact must be documented to show the date of the attempt, the party’s name and phone number, and whether or not additional information was provided.
While implementation of the Tidewater procedure has resulted in fewer requests for reconsideration of value, they do still occur and should be handled in the usual manner, as discussed on page 28. For complete and detailed instructions regarding proper use of the Tidewater Initiative, please refer to Circular 26-03-11, included in the Addenda at the end of this Handbook (see pages 90-93). "

In summary, the Tidewater procedure is a benefit to all parties to make sure the deal doesn't fall apart due to an incorrect appraisal value.