Boats:
Pope Paul VI: "The Church, nevertheless, in urging men to the observance of the precepts of the natural law, which it interprets by its constant doctrine,** teaches that each and every marital act must of necessity retain its intrinsic relationship to the procreation of human life. **This particular doctrine, often expounded by the magisterium of the Church, is based on the inseparable connection, established by God, which man on his own initiative may not break, between the unitive significance and the procreative significance which are both inherent to the marriage act.
“The reason is that the fundamental nature of the marriage act, while uniting husband and wife in the closest intimacy, also renders them capable of generating new life – and this as a result of laws written into the actual nature of man and of woman. And if each of these essential qualities,** the unitive and the procreative, is preserved,** the use of marriage fully retains its sense of true mutual love and its ordination to the supreme responsibility of parenthood to which man is called.” (Humanae Vitae, n. 11-12).
Marital Act, means sexual marital act using the genitals properly for their function. Because if you didnt use them to their proper function the act would no longer be pro-creative.
Hugging, kissing is not a sexual marital act but foreplay and affection.