Petitioners pre-employment medical examination reveals that he suffered no heart trouble nor high blood pressure and was diagnosed as fit for work (Annex B-4, p. 75, Rollo). It is not disputed that petitioners work (deck fitter) required routine hard manual labor. The extreme and hazardous working environment in the engine room tended to develop symptoms of headache, dizziness and cardiac lapses. Heeding private respondents request, petitioner also performed emergency overhauling work inside the compressor room for two weeks in time for the vessels delivery to the new owners. Inevitably, he was exposed to ammonia, causing chest pains and abnormal breathing (pp. 34-35, Rollo). Contrary to private respondents claim, petitioners strenuous work is the proximate cause of his hypertensive cardiovascular disease. Private respondents assertion that subject illness was developed after the termination of petitioners employment deserves scant consideration. Firstly, petitioner performed no strenuous work after the delivery of private respondents vessel to the new owners. Secondly, private respondents designated physician declared him unfit for sea duty on January 2, 1997 (Annex I-1). Respondent NLRCs finding that petitioner failed to show proof that his illness was work-connected, constitutes a reversible error. As heretofore elucidated, petitioners work as deck fitter and the two-week emergency overhauling job caused him to develop hypertensive cardiovascular disease. Basic is the rule that actual proof of causation is not necessary to justify compensability. Probability, not certainty, is the test. Substantial proof, not actual proof, is the requirement. To require otherwise would be inconsistent with the liberal interpretation of the Labor Code and the social justice policy of the State. Petitioners employment having been terminated due to a cause beyond his control, his services shall be deemed uninterrupted pursuant to TCC-CBA covering his employment, thus: Section 3. Service shall be deemed uninterrupted when a seaman is paid on vacation or awaiting assignment after his paid vacation, or is on leave due to medical reasons, or when the interruption is not attributable to the seamans fault or own-making. xxxxxx In fine, the Court is fully convinced that respondent NLRC did act with grave abuse of discretion in setting aside the Labor Arbiters decision. WHEREFORE, the decision appealed from is hereby REVERSED and SET ASIDE. Accordingly, the decision dated December 22, 1997 of Labor Arbiter Romulus S. Protasio is REINSTATED.