1: πλοιάριον
(Strong's #4142 — Noun Neuter — ploiarion — ploy-ar'-ee-on )

"a skiff or small boat," is a diminutive of ploion (No. 2), Mark 3:9; 4:36; John 6:22 (but No. 2 in the 2nd part of the verse), John 6:23 (here some texts have No. 2), John 6:24; 21:8 .

2: πλοῖον
(Strong's #4143 — Noun Neuter — ploion — ploy'-on )

AV, "ship," is preferably translated "boat" (RV) in the Gospels, where it is of frequent use; it is found 18 times in Acts, where, as in James 3:4; Revelation 8:9; 18:19 , it signifies a ship. See SHIP.

3: σκάφη
(Strong's #4627 — Noun Feminine — skaphe — skaf'-ay )

is, lit., "anything dug or scooped out" (from skapto, "to dig"), "as a trough, a tub, and hence a light boat, or skiff, a boat belonging to a larger vessel," Acts 27:16,30,32 .