PA-28 pilot reported losing directional control on the landing roll for unknown reasons.

Attributes
ACN	1626883
Time
Date	201903
Local Time Of Day	1201-1800
Place
Locale Reference	ZZZ.Airport
State Reference	US
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Make Model Name	PA-28 Cherokee/Archer/Dakota/Pillan/Warrior
Operating Under FAR Part	Part 91
Flight Phase	Landing
Route In Use	Direct
Flight Plan	VFR
Person 1
Function	Single Pilot Pilot Flying
Qualification	Air Traffic Control Fully Certified Flight Crew Private
Experience	Flight Crew Last 90 Days 65 Flight Crew Total 304 Flight Crew Type 129
Events
Anomaly	Ground Event / Encounter Loss Of Aircraft Control Ground Excursion Runway
Miss Distance	Horizontal 0 Vertical 0

Narrative:

This was my final landing after a week-long trip; I was coming home. As I was fifteen miles out; I received my first ATIS; winds were 080-110 @ 7kts. When I was ten miles out I listened to ATIS again; report was much of the same but winds were now at 10kts. I lined up on final; everything was normal. I landed with my main gear on the numbers; my nose gear shortly landed after that and I put my flaps up and carb heat off. As I was rolling out; my airspeed was slowing rapidly and I begin to lightly apply even brake pressure; as I have done thousands of times before. However; as soon as I [applied the brakes]; the airplane takes a severe turn (about 45 degrees according to tire marks) to the right. At this point I was traveling about 30kts and headed directly towards the marsh. I knew at this point; going into the marsh was inevitable. Instead of over-correcting and potentially flipping the airplane; I tried to keep the plane level; cut mixture and fuel pump; then I braced myself for impact. When I came to a stop; I immediately exited the aircraft and walked to FBO to call authorities.

Original NASA ASRS Text

Title: PA-28 pilot reported losing directional control on the landing roll for unknown reasons.

Narrative: This was my final landing after a week-long trip; I was coming home. As I was fifteen miles out; I received my first ATIS; winds were 080-110 @ 7kts. When I was ten miles out I listened to ATIS again; report was much of the same but winds were now at 10kts. I lined up on final; everything was normal. I landed with my main gear on the numbers; my nose gear shortly landed after that and I put my flaps up and carb heat off. As I was rolling out; my airspeed was slowing rapidly and I begin to lightly apply even brake pressure; as I have done thousands of times before. However; as soon as I [applied the brakes]; the airplane takes a severe turn (about 45 degrees according to tire marks) to the right. At this point I was traveling about 30kts and headed directly towards the marsh. I knew at this point; going into the marsh was inevitable. Instead of over-correcting and potentially flipping the airplane; I tried to keep the plane level; cut mixture and fuel pump; then I braced myself for impact. When I came to a stop; I immediately exited the aircraft and walked to FBO to call authorities.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.