Code of Civil Procedure § 318 is the basic adverse possession statute:
No action for the recovery of real property
, or for the
recovery of the possession thereof, can be maintained, unless it
appear that the plaintiff, his ancestor, predecessor, or grantor, was
seized or possessed of the property in question, within five years
before the commencement of the action
321. In every action for the recovery of real property, or the
possession thereof, the person establishing a legal title to the
property is presumed to have been possessed thereof within the time
required by law, and the occupation of the property by any other
person is deemed to have been under and in subordination to the legal
title, unless it appear that the property has been held and
possessed adversely to such legal title, for five years before the
commencement of the action.
322. When it appears that the occupant, or those under whom he
claims, entered into the possession of the property under claim of
title, exclusive of other right, founding such claim upon a written
instrument, as being a conveyance of the property in question, or
upon the decree or judgment of a competent Court, and that there has
been a continued occupation and possession of the property included
in such instrument, decree, or judgment, or of some part of the
property, under such claim, for five years, the property so included
is deemed to have been held adversely, except that when it consists
of a tract divided into lots, the possession of one lot is not deemed
a possession of any other lot of the same tract.
323. For the purpose of constituting an adverse possession by any
person claiming a title founded upon a written instrument, or a
judgment or decree, land is deemed to have been possessed and
occupied in the following cases:
1. Where it has been usually cultivated or improved;
2. Where it has been protected by a substantial inclosure;
3. Where, although not inclosed, it has been used for the supply
of fuel, or of fencing timber for the purposes of husbandry, or for
pasturage, or for the ordinary use of the occupant;
4. Where a known farm or single lot has been partly improved, the
portion of such farm or lot that may have been left not cleared, or
not inclosed according to the usual course and custom of the
adjoining country, shall be deemed to have been occupied for the same
length of time as the part improved and cultivated.
324. Where it appears that there has been an actual continued
occupation of land, under a claim of title, exclusive of any other
right, but not founded upon a written instrument, judgment, or
decree, the land so actually occupied, and no other, is deemed to
have been held adversely.
325. For the purpose of constituting an adverse possession by a
person claiming title, not founded upon a written instrument,
judgment, or decree, land is deemed to have been possessed and
occupied in the following cases only:
First--Where it has been protected by a substantial inclosure.
Second--Where it has been usually cultivated or improved.
Provided, however, that in no case shall adverse possession be
considered established under the provision of any section or sections
of this Code, unless it shall be shown that the land has been
occupied and claimed for the period of five years continuously, and
the party or persons, their predecessors and grantors, have paid all
the taxes, State, county, or municipal, which have been levied and
assessed upon such land.
You have to remove him within 5 years in my opinion.
But this sounds like it is out of hand. I don't know if the aquatter is disturbed or deluded or what exactly is going on with him but the situation is not good and should be squelched immediately. Peacefully if possible but the fact is, this sounds like trespassing and the Sheriff can be called to order a trespasser to get out and stay out.
The longer you delay, the more likely that the Sheriff will think he has some legal right to be there.