Avoid those areas when waves are large or strong currents are forced to flow over them. Waves become steeper and break on beaches and shoals. Avoid landing in surf with a loaded kayak. Avoid surf on rocky beaches. Seas become chaotic.
Cliffs limit landing sites and can cause chaotic rebounding wave conditions.
Make yourself visible and never assume you have been seen or have the right of way. Cross shipping lanes only at right angles and do so quickly. Never underestimate the speed of large ships. With the exception of the tides, large lakes pose most of the difficulties and dangers of the sea. Waves, however, are steeper and more likely to break than on the sea.