It would have been amusing if the small craft had lobbed a few cherry bombs into the water . . .
Anyway, this reminds me of a story from some years back when Soviet subs were probing Sweden's harbors. A bunch of Swedish college students got a bunch of PVC pipes (or the Swedish equivalents) and put a cap on one end and an elbow on the other. They weighted the capped end with sand or rocks as ballast, and put them in the water; the ballast kept them upright, and a good length of pipe (with the elbow on the end) stuck out above the surface - instant periscope!
They put them in the water so the current would carry them to the Swedish naval base at Karlskrona, where they caused a bit of a furor.
Swedish naval authorities were not amused.