From Longman Dictionary of Contemporary Englishheavy seasheavy seasTTWDNsea with big waves → heavy
Examples from the Corpus
heavy seas• A 20-knot northeast wind was raising heavy seas.• At the time there were very heavy seas.• In May at least 20 were reported drowned in a similar incident in heavy seas.• Search and rescue efforts were hampered Friday by rain and heavy seas.• The boat was making very slow progress in heavy seas.• The whole service has taken some five and a half hours in gale force winds and heavy seas.• Really heavy seas can force cancellation of services.• The ship went down in heavy seas off the coast of Scotland.• He treads water in heavy seas, yelling to search planes overhead. 