Kourtney Kardashian Slammed For Having Son Rocky on Boat without Life Jacket

2:24 PM PST -- Kourtney Kardashian listened to fans outraged that she'd take her toddler Rocky onto a boat with no life jacket -- 'cause she just posted that she got her little boy a brand new one!

Check out the update on her Instagram Story ... she thanked fans for their concern and admitted she "didn't think about some of the dangers" associated with boating.

She added she hopes this incident makes "other mommies aware of the dangers of certain types of boating without a life vest."

Kourtney Kardashian is in some rough waters with fans after she posted a snap of her 21-month-old son Rocky Thirteen on a boat without a life vest.

Check out the pic ... she's lounging on the back of the vessel with her little one cuddled up in her lap. It's a sweet pic -- but fans can't help but notice Rocky's got no flotation device on all while the boat is in motion!

Just check all the comments -- fans are begging KK to put a life jacket on her bundle of joy ... and in disbelief that she would post such a photo.

The snap was included in a photo dump the Lemme founder posted of a recent family trip, which let them enjoy some fresh air and boating away from the paps back in L.A.

Other pics show some of their yummy meals from the vacay, a fun tubing moment, and a selfie that depicts Kourt flaunting her curves in a nude bodysuit.

Kourtney posted the controversial boating snap on her Story as well, confirming she was breastfeeding her son while celebrating the fact that she could after doctors told her he "probably wouldn't be able to."

As you know ... the 'Kardashians' star welcomed Rocky in November 2023 with her husband Travis Barker after some fertility complications.

She's also the mom to sons Mason, 15, and Reign, 10, and daughter Penelope, 13, whom she shares with Scott Disick.

Kourtney's also a stepmom to Travis' 3 kids -- son Landon, 21, daughter Alabama, 19, and his stepdaughter Atiana, 26, whom he shares with his ex, Shanna Moakler.

TMZ reached out to Kourtney's team for comment ... so far, no word back.