The Germans used a small flat-bottomed motorised lighter or boat to move men and supplies around calmish waters - rivers, estuaries, the Baltic and Mediterranean. I-Lighters were particularly active around the Greek Islands.
I modelled these mostly using balsa wood. The original boats were around 15-18 m long so these are small models. They have a small one-barrelled automatic gun, an MG or 20mm cannon, on a mount near the bow.
I-LIGHTER Photo
This is the photo I used as a template .
These boats were involved in combat with British coastal craft in the Med.
Dutch Plan
I-Lighters were built all over Europe so they probably varied a bit. These plans are from a Dutch workshop. Note the association with Siebel.
3D image
Another take on an I-Lighter.
Underwater Wreck
A wrecked I-Lighter found by divers off Croatia. This photo shows the stem.
The Helm Position
The View Aft
The Bow
Note that the bow is detached from the rest of the hull. Apparently I-Lighters could be disassembled for transport on trains.
You can read more on the Axis History Forum.
Lake Ladoga Patrol Boat
The last I-Lighters were used by the Finns on Lake Ladoga as gun boats with a 57mm gun fitted centrally .

Finnish Gunboat Underway
Out Of The Water
Again, these photos are derived from the Axis History Forum, which is a mine of expert opinion.
Size Comparison
To show how small these craft were, here is one of my scratchbuilt models alongside an S-Boot. Both are 1:300 scale .