The bad news is, yeah, that is pretty ugly. The good news is that it won't be too hard a fix.
You've got two options, "fix" it, or repair it.
To "fix" it, you go grab a tube of real cheap silicone, and blob it on wherever water comes through.
To repair it, the process is a little more complex, but not hard.
First, remove the old patch completely. Remove all the goop. Chances are, if that much goop was needed, the patch is a poor fit, and you'll likely have to redo it. See what the hole looks like. Then, find you another piece of aluminum, .063 - .080 range, cut it to shape, where it overlaps the hole, round off the corners, then roll it around something (piece of pipe, bucket, whatever you have laying around), to match the radius of the hole. Clamp the piece to the hull. Now, break out the drill, and start drilling your holes (I'd be using 3/16 rivets, in this case). This an excellent use for cleco fasteners, but unless you do a little more metalworking than the average joe, you probably don't have these. Bolts will be a good substitute. Just as you get a hole drilled, put a bolt or something in it, to assure that all will line up. Space your holes about 1 - 1.25" on center.
Once you've drilled around the perimeter, pop the piece off, and debur all the metal. Here is where you have two options. 1st is to use pop rivets, and the second is to use solid rivets, like the boat has. For pop rivets, all you need is a 20 dollar rivet gun from Lowes or Home Depot. For solid rivets, you can get by with two heavy hammers. Place a bit of 3M 5200 around the perimeter. The goal here is to seal between the hull and the patch, not glob stuff on top like is there currently. Rivet in place. If you use solid rivets, no sealant is needed around the rivet. For pop rivets, put a dab of sealer in the hole before inserting the rivet, then put a tab in the middle of the rivet (where the mandrel was), after you pull the rivet.
The repair should last forever, the "fix," not so much.