I think plot lines and polygons are great but you have to keep in mind that "structure" can change over time. A feature that exists in one year can cease to exist in another. So I would suggest some method of aging and archiving the trip details that change over time so that they don't continue to mislead users researching a particular fishing spot.
might be a good idea to limit what guests can see. They should not be able to see trips and get info without at least becoming a member