TWO BELL 206'S (N3913Z OPRD BY HELITRANS, N5759Y OPRD BY ISLAND EXPRESS) DEPTD AVALON 2 MIN APART ON FLTS TO SAN PEDRO. ARR ROUTE AT DESTN WAS OVR A RVR WITH ANGLING FNL APCH ARND A FLOATING RESTAURANT (FR). HELIPORT (HP) WAS IN CONGESTED AREA NR BRIDGE, BLDG, BOAT DOCK. EACH PLT MADE REQD RDO CALL ON UNICOM FREQ, 2.5 MI OUT; CHNGD TO 123.30 MHZ BTN RVR MOUTH & HP TO CHK ON FLYING AT ANOTHER OPR'S LOCATION; CHNGD BACK TO UNICOM; EXCEPT PLT OF N5759Y ALSO CHKD IN ON HIS COFREQ. AS 1ST FLT (N3913Z) ARR, BOAT WAS DOCKING; PLT MADE GO-ARND, BUT DIDN'T MAKE RDO CALL. AS N3913Z WAS ON 2ND APCH, N5759Y CONVERGED FM DRCTN OF SETTING SUN IN L TURN ARND FR & ACFT COLLIDED. NEITHER PLT CALLED FNL APCH. N5759Y CRASHED IN WTR; N3913Z HIT EDGE OF HP, ROLLED OVR. PAX IN N5759Y HAD PRBLM EGRESSING; INADEQ BRIEFING BFR FLT. HP OWNER (LA PORTAUTHORITY) DIDN'T PROVIDE RSTRCTNS OF OPRG PERMITS TO OPRS. OPRS DIDN'T ABIDE BY HP OWNER'S 5 MIN SEPN RULE. MIN OVRSGHTBY FAA & CA DEPT OF AERONAUTICS. PLT OF N3913Z LACKED 10 HRS OF REQD TRNG. THE HP WAS CERTIFIED FOR SEAPLANE OPN.