They're Playing with Fire (1984)

A married college professor embarks on a forbidden affair with her young, hesitant student, who doubles as her yacht's handyman. Their passionate romance kindles a dangerous game, as a corrupt husband and a masked murderer threaten to extinguish their fiery desires, setting the stage for a scorching tale of lust, betrayal, and suspense on the high seas.
• Tags: seduction, forbidden, love, affair, suspense, betrayal, murders, corruption