Gaza's Health Ministry said 32 Palestinians were wounded by Israeli fire during a mass protest along the beach near the Israeli frontier.
Protesters threw flaming tyres over the border fence, while fishing boats hoisted Palestinian flags and circled near the shoreline. Israeli forces responded with tear gas and live fire.
The ruling Hamas militant group has been staging border protests for the past six months in hopes of easing a crippling Israeli-Egyptian blockade.
It has intensified the protests in recent weeks as Egyptian-mediated cease-fire efforts have faltered.
Since March, 155 Palestinians participating in or attending the protests have been killed, while one Israeli soldier was fatally shot in July.