If your into player controled ships, boats and sea planes and you want to use them in missions. To start on the water with out creating a special sea base you can create a sea plane tender, which is simply any suitable ship with the ship .cfg modified to make it a carrier but the flight deck is off set and placed at sea level. Now you place the tender in the mission where you you want to start and bobs your uncle. 
heres a copy of the file use it with any ship model you like

[fltsim.0]
title=Sea_Plane_Tender
sim=Sea_Plane_Tender
model=
panel=
sound=
texture=

[flight_deck_section]
; this section defines the control points the
; AI (and LSO) use to steer towards the flight deck
width=20
length=30
takeoff_start=50.0,0,-50
takeoff_stop=50.0,0,50
landing_start=100,500,-1600
landing_touch_down=100,0,-600
landing_stop=100,0,0

[platform.0]
; platforms are the actual surface that the planes
; land on.  You can define as many platforms as you
; want by adding subsequent sections with increasing
; numbers.  e.g. [platform.1], [platform.2] etc.
;
; vertices should be defined in model coordinates,
; and counter-clockwise order when viewed from above.
: REMEMBER, positive z is out the TAIL of the ship
; the shape may be concave or convex
; there may be from 3 to 20 vertices (limitation
; may go away later) and they must all be on the same
; plane.


vertex.0=5.450,10.150,81.90
vertex.1=5.450,10.150,45.80
vertex.2=-5.450,10.150,45.80
vertex.3=-5.450,10.150,81.90

[Dynamics]
pitch_wave_moment_scale = 1
bank_wave_moment_scale  = 1
pitch_damp_moment_scale = 1
bank_damp_moment_scale  = 1