I would add a couple of simple hats with wide brims and rudimentary sunglasses. At least a couple per raft so those standing watch could more effectively and safely get out from under the canopy and see what is going on.

The hat could be any design that would store compactly and keep the sun off the head and shield the face and neck. A light color and broad brim would be ideal in sunny climates.

The sunglasses could be the simple dark, one-piece, polarized units that are stamped out of single sheet of dark plastic. These are often seen as give-away glasses at opthalmology clinics. Being a single piece of plastic and quite flat when not being worn a few pairs could be slipped in virtually any kit.

You need someone to keep watch if for no other reason than to maintain a sense of purpose and to know when it is best to use the limited supply of flares and markers. Trying to keep watch over water without a decent hat and sunglasses in the tropics is just about futile. The sun bakes your brain and the glare blinds you. Stare into the glare enough and you can seriously harm the eyes. Polarized glasses would also be helpful when fishing because they allow you to see beneath the surface.

Another consideration would be to have a supply of simple light colored bandannas or triangular bandages available. These can be rigged as simple head covers, shields to keep the sun off the neck or face, expedient bandages or tourniquets, lashings for equipment, cleaning cloths, sponges, place mat, or tied into a small sack to help organize small gear.

A cloth as large as a typical non-sterile triangle bandage, about $.25 in bulk, has lots of uses. In my first-aid kit I have replaced some of the gauze rolls and general bandaging materials with a couple of triangle bandages. In a pinch a triangular bandage can still be used as a compress or wrap but it has a lot more potential uses.