Tom Brady to Son -- KNEES HIGH ... Father/Son Drills at the Beach!

With the combine underway in Indianapolis, the biggest NFL prospect of them all was training hard on the beach with his dad in California ... and we've got the pics.

Tom Brady and his 4-year-old son Ben were running drills in Santa Monica this week -- with Tom even breaking out the cones to add to the workout.

No word if Ben's received any scholarship offers yet ... but with only 14 years to go until his freshman season, it's never too early to start recruiting ... right Alabama?