They look pretty much like the modern CG/USN interdiction boats used for harbor security and the like.
Best PBR EVAH! [was] SBU 26's MkIVs in the Panama Canal, 40 foot aluminum hulled twin MONSTER engines (12 cylinder diesels, IIRC), Mk 19 40 mm grenade launchers, .50s, lotsa firepower hanging off the squids in the form of M16s and M203s. Watched a Chief Boatswain walked one sideways across a lock in the canal, this guy never went more than 4-6 inches fore and aft to do it.
ETA: I wasn't really looking close at the picture when I found it on the web: the boat behind the Mk IV is a USCG 110' Island class patrol boat. Took me a long time to identify it, because I was unaware that any had been in the Ditch at the same time as the Mk IVs. The fastest transit that I ever made of the Panama Canal was while seated at the crosstree (just to the left of the helmeted sailor in the photo seated on top of the Mk IVs cabin) and repairing the AB-1248/U radar antenna pedestal there. (The antenna is end on in this picture.) Transit time was just over 40 minutes.