Possible Clues:

• Suffering from mal-de-mer
• Nauseous from the rolling of a ship
• Needing Dramamine, maybe
• Feeling discomfort in waves
• Queasy on board
• Second rock cake is liable to produce vomit
• Not enjoying the whale watch, maybe
• Suffering from mal de mer
• Nauseous on the briny
• This makes one throw it up on board