Anchor recommendations for grassy flats

Been using a 3# folding grapnel anchor for my yak with good results or the most part.

Now that I have a little heavier yak and need another anchor, wanted to get some input.

The grapnel anchor works best in the marsh where it's too deep for my Cajun anchor. But sometimes it's not effective when I fish sandy bottom flats.

So all that being said, I guess my question is what's the best type and weight anchor for fishing sandy bottom grass flats no more than 8' deep for a yak? (Weight loaded down about 350#)