On January 19, about 0800 Pacific standard time, a Piper PA-28R-200, N57355, was substantially damaged when it was involved in an accident near Carlsbad, California. The flight instructor, pilot receiving instruction (pilot), and passenger were not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 instructional flight. The flight instructor stated that they planned a flight to Santa Ana, California, for the pilot to accumulate flight time in the accident airplane. The preflight inspection was normal and showed that the oil sump contained about 6 quarts of oilI. After an uneventful engine run-up, they departed the airport and turned right to a northerly heading after they climbed to about 2,500 ft mean sea level (msl). As the airplane reached about 3,200 ft msl, the instructor observed that the oil pressure gauge indicated a pressure below “0 psi,” while the oil temperature remained in the normal range. The instructor notified ATC and informed them that they were deviating to a nearby airport. While the pilot attempted to maintain 3,000 ft msl, the instructor observed the propeller default to maximum rpm and anticipated that the engine would soon fail. A few minutes later, the instructor observed smoke coming into the cockpit through the defrosters, accompanied by a faint oil smell. He then heard a loud sound from the engine compartment and observed the propeller stop turning, which was accompanied by smoke coming from the engine cowling. After a brief discussion, the pilots decided to perform a water landing. The pilot flew the airplane to the surface. The instructor notified ATC of the engine failure and intended landing site. They subsequently touched down about 50 yards from the shoreline with the landing gear up. A review of the airplane maintenance records revealed that an annual inspection was completed on September 15, 2022, about 4 months before the accident. The engine had been removed from the airplane and overhauled in November of 2016. At the last annual inspection, the engine had accumulated about 1,280 hours since overhaul. Postaccident examination of the airplane revealed the left wing fractured and separated about mid span. Buckling and bending was observed on the fuselage aft of the wings. Damage to the right wing was observed about mid span. Examination of the engine revealed that it remained attached to the engine mounts. The engine was exposed to salt water during the accident and contained rock debris from impact with terrain. All the engine accessories remained attached to their respective mounting pads and no loose wiring or fluid leakage was observed throughout the engine. The engine case was breached been the push tubes of the No. 2 cylinder, showing a visible puncture along the push-pull tube channel. A mixture of oil, water, and sand was observed on the engine oil dipstick. The oil sump was attached to the engine case and was severely corroded due to saltwater exposure/submersion. A hole about 3 inches wide was observed in the oil sump below the No. 2 cylinder induction tube connection. The area was white, consistent with saltwater corrosion, and the area was soft and was easily penetrated when pressure was applied. The No. 1 cylinder was removed to facilitate internal examination of the engine crankcase. Internal examination of the engine revealed that the No. 2 connecting rod separated from the crankshaft and a small portion of the connecting rod end cap (No. 2 cylinder) remained attached to the rod shank. Rotational score marks were observed along a visible portion of the camshaft at the No 2 cylinder connecting rod. A heat gradient was observed along the shank of the No. 2 cylinder connecting rod, consistent with thermal stress. The No. 2 connecting rod bearing had separated from the journal, which was mechanically damaged. A remaining section of the connecting rod end cap displayed score marks consistent with interfacing at the No. 2 crankshaft journal. A subsequent engine examination revealed the crankshaft main bearings were intact and showed normal operational wear. The crankcase halves showed no signs of fretting or main bearing shift in the bearing saddle areas. The crankcase oil galley plugs were removed, and the oil galleys were free from obstruction. The No. 1, 2, and 3 connecting rod bearings had thermal discoloration and metal deformation. The crankshaft oil galleys were clear of obstructions. The center bearing exhibited evidence of thermal distress and rotational scoring. The pushrods remained intact except for the cylinder 2 pushrods, which were damaged during the engine’s exposure to saltwater after the accident. The intake and exhaust valves for cylinder Nos. 2 and 4 could not be inspected due to damage sustained during postaccident exposure to saltwater. Each rocker arm was securely attached at its respective cylinder and to its valve. The engine was mostly devoid of oil. The oil return line at the No. 3 cylinder contained oil sludge as did the oil sump, which also exhibited evidence of saltwater corrosion. The accessory housing was mostly unremarkable, with exception of the oil pump, which exhibited heavy resistance when rotated by hand. The pump gears and housing contained oil throughout along with non-ferrous fragments, sludge along the track of the gears, and rust on one of the gears. The oil pump turned normally after the gears and housing were cleaned. No obstructions were observed in either of the two oil galleys.